11 - The Breast and the Physiology of Lactation

163

Universal breastfeeding is recommended by the American

College of Obstetricians and Gynecologists (ACOG), the World

Health Organization (WHO), the United Nations Children’s

Fund (UNICEF), the American Academy of Pediatrics (AAP),

and the Special Supplemental Nutrition Program for Women,

Infants, and Children (WIC), but recommendations alone are

not sucient to promote breastfeeding. It is the responsibility

of every physician to recommend and promote breastfeeding

enthusiastically and support the breastfeeding mother- infant

dyad with informed, applicable, evidence- based medicine. is

is especially true in obstetrics, where a physician’s advice can

immediately inuence a woman’s informed decision concerning

breastfeeding and create or diminish barriers to successful

breastfeeding.

Benefits of Breastfeeding

Breastfeeding provides signicant benets for both the mother

and the infant. A number of these benets are documented

in an evidence- based analysis in the Agency for Healthcare

Research and Quality (AHRQ) report on breastfeeding

in developed countries.

1,2

ACOG and other groups have

championed the benets of breastfeeding and the use of human

milk.

3- 6

e benets are so signicant that the AAP and ACOG

recommend exclusive breastfeeding for the rst 6 months of life

and continued breastfeeding through 12 months or more.

e

WHO recommends that mothers initiate breastfeeding within 1

hour of birth and provide exclusive breastfeeding for the rst 6

months of life to achieve optimal infant growth, development,

and health; subsequently, to meet their evolving nutritional

requirements, infants should receive nutritionally adequate and

safe complementary foods, while continuing to be breastfed for

up to 2 years or beyond.

Breast milk is species specic, made uniquely for the human

infant.

Protein in breast milk is readily digested and is present

in amounts that can be handled by the developing kidney.

Various minerals (e.g., iron) and nutrients exist in a form

and in conjunction with other components that make them

easily absorbed to meet infants’ needs during periods of rapid

growth.

9,10

Cholesterol and docosahexaenoic acid have been

shown to play a role in central nervous system development

and may contribute to the enhanced intelligence quotient

measurements reported in breastfed infants.

11- 14

Protection against infections, including otitis media, croup,

pneumonia, and gastrointestinal infections, is mediated by the

over 50 immunologically active components found in breast

milk.

9,15- 17

ese immunologically active components include

viable functioning cells (T and B lymphocytes, macrophages),

T cell–secreted products, immunoglobulins (especially secretory

immunoglobulin A [IgA]), carrier proteins such as lactoferrin

and transferrin, enzymes (lysozyme and lipoprotein lipase),

and nonspecic factors such as complement, bidus factor,

gangliosides, oligosaccharides, and nucleotides. Other immune

factors in breast milk include hormones, hormone- like factors,

and growth factors that contribute to the normal maturation of

the mucosal barrier of the respiratory and gastrointestinal tracts

as well as the developing infant’s immune system. Breast milk

is a very dynamic uid, varying with the mother- infant dyad’s

environment and needs, especially in the face of infection or

stress (providing, e.g., leukocytes, nucleotides, oligosaccharides,

secretory IgA, interleukin, interferon, and cytokines).

16- 21

ere

is also evidence that breastfeeding provides protection against

some noninfectious illnesses such as asthma, eczema, childhood

lymphoma, insulin- dependent childhood- onset diabetes, and

obesity

16,22- 27

in children who are exclusively breastfed for the

rst 4 to 6 months of life. A cohort study of infants in Australia

and a meta- analysis

showed lower odds of developing type 1

diabetes and type 2 diabetes, respectively.

Cognitive and psychological benets for breastfed infants

have been suggested, including those for developmental

performance,

visual acuity,

31- 33

school performance,

and performance on standardized and intelligence quotient

tests.

More recent articles continue to support the impact

of breastfeeding on intellectual development while fostering

debate over the relative contributions of nutrition, genetics,

and environment to the intellectual development of infants and

the possible inuence on the child’s or adult’s future cognitive

abilities as measured by intelligence quotient testing.

13,36,37

e

psychological benets are more dicult to measure but are

well described by Newton and Newton

and, indeed, by most

mothers who have successfully breastfed their infants.

One

of the most consistent ndings of exclusive breastfeeding is its

inuence on later intelligence, with a few test points’ advantage

to the breastfed infant.

Reports questioning this eect have

been based on heterogenous denitions of breastfeeding (any

breastfeeding, not exclusive breastfeeding) and may not have

controlled for all potential confounders.

Potential benets to the mother in the short term

include improved postpartum recovery,

a decreased risk

of postpartum hemorrhage,

and prolonged amenorrhea

in mothers who exclusively or predominantly breastfeed in

the rst 6 months postpartum, which may increase spacing

between births.

ere are data supporting the psychological

benets of breastfeeding for the mother, but there are also

some equivocal studies. e relationship between breastfeeding

and postpartum depression is complicated. Prenatal and

The Breast and the Physiology of

Lactation

ADETOLA LOUIS- JACQUES, MD | ROBERT M. LAWRENCE, MD | RUTH A. LAWRENCE,

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164

postpartum depression are associated with early cessation of

breastfeeding.

Among women without a prenatal diagnosis

of depression, high positive emotions during infant feeding at

2 months were associated with lower depression and anxiety

symptoms at 2, 6, and 12 months.

In contrast, breastfeeding

worries, lower breastfeeding self- ecacy, negative breastfeeding

attitudes, breastfeeding challenges, and pain have increased risk

of developing postpartum depression.

Long- term benets of lactation include a reduced incidence

of metabolic syndrome, hypertension, type 2 diabetes mellitus,

and breast and ovarian cancers.

1,4,6,46- 49

Bone metabolism

changes during pregnancy and lactation to meet the needs of the

mother and infant. Specically, during lactation, maternal bone

resorption occurs to meet the demand for calcium, although

these bone losses are reversed over time.

Feltner and colleagues

reviewed the risk of fractures rather than the risk of bone mass

loss.

ey identied that many variables may contribute

to the risk of fractures (age, hormone replacement therapy,

physical activity, parity, and body mass index [BMI]) related

to lactation. ey concluded that no studies demonstrated a

signicant association between breastfeeding and fracture. Most

of the studies described a lower odds of fracture with greater

breastfeeding duration that was not statistically signicant.

Increasing number of pregnancies, longer oral contraceptive use,

and increasing duration of lactation are all protective against

ovarian cancer.

51- 53

e incidence of breast cancer is lower among

women who have nursed.

54,55

Newer data show an association

between breastfeeding and lower rates of diabetes,

56,57

and for

women with gestational diabetes who breastfeed there is lower

risk of developing type 2 diabetes in the postpartum period.

Endometrial and thyroid cancers have also been reported to

be lower in breastfeeding mothers.

59,60

Other benets include

lower cost of providing adequate infant nutrition and lower

environmental costs: 6 months of breastfeeding saves between 95

and 153 kg of CO

compared with formula feeding.

61,62

ere is a dose- response relationship between the amount

of human milk received by an infant and the benets or

immunologic protection gained. e health benets to

the mother from breastfeeding also relate to the dose and

duration of breastfeeding. e relative “dose” of breastfeeding

has been dened in terms of exclusivity versus the amount of

supplementation (Table 11.1).

e WHO provides a specic

denition of exclusive breastfeeding: “Exclusive breastfeeding

means that the infant receives only breast milk. No other liquids

or solids are given – not even water – with the exception of oral

rehydration solution, or drops/syrups of vitamins, minerals or

medicines.”

e importance of this dose- response relationship

is emphasized in the AAP’s and ACOG’s recommendation for

exclusive breastfeeding in the rst 6 months of life and the

AHRQ report’s analysis of the benets of breastfeeding relative

to measured durations of breastfeeding.

1- 4,6- 8

It is essential that a discussion of the benets of breastfeeding

for families (fathers and partners included) be presented

alongside any potential risks or contraindications. e

benets of breastfeeding are tremendous, and the risks and

contraindications are few. Summarized here and in Table

11.2 are the conditions in which the risks of breastfeeding or

providing expressed mother’s own milk to infants may outweigh

its benets.

•

Women who take illicit drugs, abuse legal substances, or

do not control their alcohol intake and are not in stable

substance abuse treatment.

66,67

Various groups (AAP,

ABM, ACOG, NIH/LactMed, WHO) dene abuse, use

disorders, and excess consumption/lack of control of

intake based on the specic substances.

6,68- 70

•

A woman who has an infant with classic galactosemia,

because both human and cow’s milk exacerbate the con-

dition. A lactose- free formula is recommended for these

infants. In milder forms of galactosemia, partial breast-

feeding is possible.

•

Women who are infected with human immunodeciency

virus or human T- cell leukemia virus type I (see Maternal

Infections During Breastfeeding in this chapter).

•

Women who have active untreated tuberculosis. Because

of the increased risk of airborne transmission associ-

ated with the close contact that is typical of breastfeed-

ing, women with active tuberculosis should not feed their

infant by any method until treatment is initiated. However,

infected women can provide their pumped milk to their

infants (see later).

•

Women who are known or suspected to be infected with

Ebola virus, Marburg virus, Lassa virus, or dengue virus,

when a safe alternative food source is readily available (see

later).

•

Women who take certain medications (see Medications

While Breastfeeding, later).

Medical situations that indicate a potential risk from

breastfeeding must be weighed against the potential benets for

both mother and infant.

Some of the contraindications may be permanent or

temporary. For those infections with predominantly airborne

or contact precautions, expressed milk may still be given to

Breastfeeding Deﬁnitions

Definition

Amount of Supplementation

Full breastfeeding Exclusive human breast milk only Infant ingests no other nutrients, supplements, or liquids

Almost exclusive No milk other than human milk; only minimal amounts of other substances

such as water, juice, tea, or vitamins

Partial breastfeeding High partial Nearly all feeds are human milk (at least 80%)

Medium partial A moderate amount of feeds are breast milk, in combination with other

nutrient foods and nonhuman milk (20%–80% of nutritional intake is

human breast milk)

Low partial Almost no feeds are breast milk (less than 20% of intake is breast milk)

Token breastfeeding Breastfeeding primarily for comfort; nonnutritive, for short periods of time,

or infrequent

Never breastfed Infant never ingested any human milk

Modiﬁed from Labbok M, Krasovec K. Toward consistency in breastfeeding deﬁnitions. Stud Fam Plan. 1990;21(4):226–230.

TABLE

11.1

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11 The Breast and the Physiology of Lactation 165

the infant. When mothers need to temporarily discontinue

breastfeeding, instructions should be provided on when and

how to resume breastfeeding, and lactation support should be

provided to help with maintenance of their supply.

ROLE OF THE OBSTETRICIAN IN PROMOTING

BREASTFEEDING

Obstetricians have many responsibilities for breastfeeding,

including the following:

•

Enthusiastically promoting and supporting breastfeed-

ing, based on the published literature of its benets advo-

cated by the major pediatric, obstetric, and women’s health

organizations.

4- 6,71,72

•

Imparting clinical information to the lactating mother

about the physiology of lactogenesis and lactation, before

and aer the birth.

•

Developing and supporting hospital policies that facilitate

breastfeeding and actively remove any barriers to it.

•

Supporting community eorts to provide women with

adequate information to make an informed decision about

breastfeeding, including links to community breastfeeding

resources.

•

Providing balanced anticipatory guidance and lactation

support to mothers and families regarding potential con-

cerns during labor, delivery, the postpartum period, and

breastfeeding (e.g., antenatal consultation with a breastfeed-

ing medicine specialist or lactation specialist for anticipated

needs such as suspected fetal cle palate, multiple gestation,

prematurity, and prior breast reduction surgery).

•

Actively assessing women for potential breastfeeding chal-

lenges, especially those with high- risk pregnancies. Be

prepared to fully evaluate and manage breastfeeding dif-

culties mothers encounter, personally or with the assis-

tance of a breastfeeding medicine specialist or lactation

specialist. Enabling breastfeeding in this at- risk popula-

tion may ameliorate cardiometabolic disease trajectories

in the mother and child dyads.

•

Providing additional breastfeeding support for mothers

at increased risk of low or insucient milk production or

other breastfeeding challenges.

•

Proactively providing equitable lactation care address-

ing potential social challenges to initiating and continuing

breastfeeding through the individual attention of the obste-

trician and the coordinated and collaborative eorts of insti-

tutional and community- based lactation support teams.

•

Fostering a general acceptance of breastfeeding by promot-

ing a normative portrayal of breastfeeding and supporting

the provision of sucient time and facilities in the workplace.

•

Performing breast examinations before and aer the birth

and emphasizing lactation as the primary function of the

breast.

•

Participating in breastfeeding education in medical and

other health profession schools.

•

Supporting breastfeeding within their own medical facili-

ties by instituting the “Ten Steps to Successful Breastfeed-

ing” as outlined by UNICEF/WHO

(Box 11.1).

e mother’s plan for infant feeding should be addressed early

in prenatal care, with counseling, a medical history focused on

breast health and breastfeeding, and a physical examination of

the breast. An outline for breastfeeding promotion in the prenatal

setting is provided in the Academy of Breastfeeding Medicine’s

Clinical Protocol #19.

Counseling can be modeled aer “e

Best Start ree- Step Counseling Strategy”

as suggested by

Lazarov and Evans.

is strategy advises beginning with open-

ended questions about breastfeeding. An acknowledgment that

feelings of doubt about the ability to breastfeed successfully are

normal is a good place to begin. Education about breastfeeding

then continues with discussion of how others have dealt with

these concerns. is conversation will elucidate much about the

woman’s knowledge of breastfeeding, her previous experiences

with breastfeeding, and her own attitudes and those of the

mother’s partner, the extended family, and other potentially

supportive persons in the mother’s life. To be respectfully

inclusive of all parents/families and avoid one example of

discrimination and inequity as experienced by the LGBTQ+

community, arming health care should begin with arming

names, pronouns, and consideration of the experiences and

opinions of both parents. e Academy of Breastfeeding

Medicine (ABM) provides some guides for providing arming

lactation care to LGBTQ+ patients and families.

To support breastfeeding optimally, the concerns of family

and friends must be addressed actively to foster needed support

Contraindications to Breastfeeding and or

Feeding of Breast Milk

Mothers should NOT

breastfeed or feed

expressed breast

milk to their infants

•  Classic galactosemia in the infant

•  Mother actively using illicit street

drug, such as PCP or cocaine

•  Mother infected with HIV,

human

T- cell lymphotropic virus type I or

type II

•  Mother with conﬁrmed or

suspected Ebola virus disease

Mothers should

temporarily NOT

breastfeed or feed

expressed breast

milk to their infants

•  Mother is infected with untreated

brucellosis

•  Mother is taking certain

medications; e.g., certain

chemotherapies

•  Mother is undergoing diagnostic

imaging with radiopharmaceuticals

•  Mother has an active herpes

simplex virus infection with lesions

present on the breast (transmission)

 • May feed or provide expressed

milk from the unaffected breast

provided the lesions on the

affected breast are covered

 • May resume feeding or providing

expressed milk from the affected

breast once the lesions have

resolved

Mothers should

temporarily NOT

breastfeed, but CAN

feed expressed

breast milk

•  Mother has untreated, active

tuberculosis

 • May resume breastfeeding after

2 weeks of appropriate treatment

and no longer contagious

•  Mother has active varicella that

developed within 5 days prior or 2

days after delivery

HIV recommendation only applies to the speciﬁc countries that

have recommended this as a component of their national efforts at

perinatal HIV transmission prevention (e.g., United States, Canada,

United Kingdom, and Italy, among others).

Data from Centers for Disease Control and Prevention.

Contraindications to Breastfeeding or Feeding Expressed Breast

Milk to Infants. Updated 2018. https://www.cdc.gov/breastfeeding/

breastfeeding- special- circumstances/contraindications- to-

breastfeeding.html.

TABLE

11.2

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PART 1 Scientiﬁc Basis of Perinatal Biology

166

on many levels. Misconceptions and potential barriers must be

identied and reasonable solutions developed in partnership

with the woman. ese oen include feelings of responsibility

for every unexplained problem the infant displays; conicts

among a woman’s several roles as mother, sexual partner, and

worker outside the home; and, most commonly, a greater time

commitment and fatigue than was expected. It is important

to address these and other questions repeatedly throughout

pregnancy and not just in the immediate postpartum period,

working closely with the infant’s pediatrician.

5,74

Dr. Alison

Stuebe, a maternal- fetal medicine expert and a member of

the Academy of Breastfeeding Medicine, utilizes open- ended

questions following a format recommended by Duggan

and Street that encompasses relational functions (fostering

healing and validating and responding to patient emotions) of

provider- patient communication and “task- driven” functions

(exchanging and managing information, making treatment

decisions, enabling patient self- management, and managing

uncertainty) to approach maternal and familial recurring issues

and concerns regarding breastfeeding.

80,81

It is important to be familiar with and in communication

with members of the medical team who support breastfeeding

throughout the community including lactation consultants,

pediatric practices, and support groups. Specic codes from

the International Classication of Diseases, 10th Revision

(ICD- 10) commonly used for breastfeeding care and breast

abnormalities are listed by ACOG to facilitate billing for

the time required for informed medical care and eective

communication.

Examination of the Breast

e medical history related to the breasts should include their

development, previous experience with breastfeeding, systemic

illnesses, infections, breast surgery or trauma, medications,

allergies, self–breast examinations and ndings, and any

anatomic or physical concerns the mother has about her breasts.

e breast examination at prenatal and postpartum visits should

include careful inspection and palpation. Inspection of the breasts

is most eective in the sitting position, rst with the arms overhead

and then with the hands on the hips. Skin changes, distortions in

shape or contour, and the form and size of the areola and nipple

should be noted. Palpation can begin in the sitting position, looking

for axillary and supraclavicular adenopathy. Palpation in the supine

position is easier for the complete examination of the breast and

surrounding anterolateral chest wall. Size, shape, consistency,

masses, scars, tenderness, and any abnormalities can be noted

in both descriptive and picture form for future comparison.

Serial examinations should document maturational changes of

pregnancy (size, shape, fullness, enlargement of areola) and nipple

position (inversion or eversion).

e changes in the breast during pregnancy provide

important prognostic data regarding successful breastfeeding.

With the increased frequency of cosmetic breast surgery, it

is important to be aware of the nature of any surgery and to

examine carefully for the location of the surgical scars. Many

women successfully breastfeed aer surgery for benign breast

disease, breast augmentation, or breast reduction. However,

a periareolar incision or “nipple translocation technique” for

breast reduction can damage nerves and ducts, making this

more dicult. Nipple piercing is another increasingly common

procedure, aer which breastfeeding can be successful with the

jewelry removed. Such surgeries do not preclude successful

breastfeeding but rather remind us that additional early support

should be provided to these mothers from physicians, nurses,

lactation consultants, and peer support groups.

Perinatal Period

e obstetrician can make important contributions to successful

breastfeeding through the conduct of the labor, delivery, and

puerperium. A stressful or exhausting labor and delivery has

been shown to aect lactation adversely.

A safe delivery for both

mother and infant is, of course, the most important outcome.

During the delivery and aerward, any medications used should be

compatible with breastfeeding and not interfere with the bonding

and rst feeding. Immediate skin- to- skin contact between mother

and infant and a rst feeding within 1 hour of delivery are probably

the most important intrapartum steps to increase the likelihood of

successful breastfeeding. Having the infant in the mother’s room,

feeding on demand, and early breastfeeding support (including

teaching appropriate techniques) within the rst 24 to 36 hours

can also help. Supplementation should be avoided unless medically

indicated and ordered by the pediatrician.

For the breastfeeding woman, medication choices are

very important (see Medications While Breastfeeding in this

chapter). Most women and many health professionals assume

that no medication can be safely administered to a lactating

woman, but the number of contraindicated drugs is in fact quite

small. Before assuming a medication is unsafe, expert advice

should be consulted, available in texts, websites, or through

drug information telephone services. (e.g., LactMed, Infant Risk

Center, MotherToBaby Call Center).

69,84,85

CRITICAL MANAGEMENT PROCEDURES

1a. Comply fully with the International Code of Marketing of

Breast- milk Substitutes and relevant World Health Assembly

resolutions.

1b. Have a written infant feeding policy that is routinely com-

municated to staff and parents.

1c. Establish ongoing monitoring and data- management systems.

2. Ensure that staff have sufﬁcient knowledge, competence,

and skills to support breastfeeding.

KEY CLINICAL PRACTICES

3. Discuss the importance and management of breastfeeding

with pregnant women and their families.

4. Facilitate immediate and uninterrupted skin- to- skin contact

and support mothers to initiate breastfeeding as soon as

possible after birth.

5. Support mothers to initiate and maintain breastfeeding and

manage common difﬁculties.

6. Do not provide breastfed newborns any food or ﬂuids other

than breast milk, unless medically indicated.

7. Enable mothers and their infants to remain together and to

practice rooming- in 24 hours a day.

8. Support mothers to recognize and respond to their infants’

cues for feeding.

9. Counsel mothers on the use and risks of feeding bottles,

teats, and paciﬁers.

10. Coordinate discharge so that parents and their infants have

timely access to ongoing support and care.

From UNICEF/WHO. The ten steps to successful breastfeeding.

https://www.who.int/activities/promoting- baby- friendly- hospitals/

ten- steps- to- successful- breastfeeding. Accessed January 28, 2021.

BOX 11.1 THE TEN STEPS TO SUCCESSFUL

BREASTFEEDING

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11 The Breast and the Physiology of Lactation 167

Early follow- up (2 to 4 days aer discharge) with the infant’s

health provider should be arranged for all breastfeeding

mothers. Continued support of breastfeeding for the mother

should occur through the 6- week postpartum visit. Discussions

about breastfeeding should cover techniques to ensure adequate

emptying of the breast as well as problems such as nipple soreness

or trauma, plugged duct (in the form of a small lump), mastitis,

breast abscess, breast masses, and bloody nipple discharge, all

of which can usually be treated without stopping breastfeeding.

The Breast

To fully understand the process of lactation, one needs to

understand the anatomy and physiology of the breast as it applies

to this function. e human mammary gland is the only organ

that does not contain all of the rudimentary tissues at birth.

It experiences dramatic changes in size, shape, and function

from birth through menarche, pregnancy, and lactation and

ultimately during involution. e three major phases of growth

and development before pregnancy and lactation occur in utero,

during the rst 2 years of life, and at puberty (Fig. 11.1 and Table

11.3).

EMBRYONIC DEVELOPMENT

e milk streak appears in the fourth week of gestation when

the embryo is approximately 2.5 mm long. It becomes the milk

line, or milk ridge, during the h week of gestation (2.5 to 5.5

mm). e mammary gland itself begins to develop at 6 weeks

of embryonic life, and proliferation of the milk ducts continues

throughout embryonic growth and again in pregnancy and

lactation. e process of forming the nipple in the human

embryo begins with a thickened, raised area of ectoderm in the

region of the future gland by the fourth week of pregnancy. is

thickened ectoderm becomes depressed into the underlying

mesoderm and thus the surface of the mammary area soon

becomes at and nally sinks below the level of the surrounding

epidermis. e mesoderm that is in contact with the ingrowth

of the ectoderm is compressed, and its elements become

arranged in concentric layers that at a later stage give rise to the

gland’s stroma. By dividing and branching, the ingrowing mass

of ectodermal cells gives rise to the future lobes and lobules, and

much later to the alveoli.

By 16 weeks’ gestation in the fetus, the branching stage has

produced 15 to 25 epithelial strips that represent the future

secretory alveoli. By 28 weeks’ gestation, placental sex hormones

enter the fetal circulation and induce canalization in the fetal

mammary tissue. e lactiferous ducts and their branches are

developed from outgrowth in the lumen. ey open into a

shallow epidermal depression known as the mammary pit. e

pit becomes elevated because of mesenchymal proliferation,

forming the nipple and areola. An inverted nipple is the failure

of this pit to elevate.

At 32 weeks’ gestation, the lumen has

formed in the branching system, and by term there are 4 to 18

ABCDE

Figure 11.1 Female breast from infancy to lactation, with corresponding duct structure and tissue cross sections. (A–C) Gradual development

of the well- differentiated ductular and peripheral lobular- alveolar system. (D) Ductular sprouting and intensiﬁed peripheral lobular- alveolar develop-

ment in pregnancy. Glandular luminal cells begin actively synthesizing milk fat and proteins near term; only small amounts are released into the lumen.

(E) With postpartum withdrawal of luteal and placental sex steroids and placental lactogen, prolactin is able to induce full secretory activity of alveolar

cells and release of milk into alveoli and smaller ducts. (From Lawrence RA, Lawrence RM. Breastfeeding: A Guide for the Medical Profession. 7th ed.

St Louis, MO: Mosby; 2010:43.)

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PART 1 Scientiﬁc Basis of Perinatal Biology

168

mammary ducts that form the fetal mammary gland.

Fig. 11.2

shows the hormonal regulation of mammary development in

the mouse.

e nipple, areola, and breast bud are important landmarks

for the determination of gestational age in the newborn. At 40

weeks, the nipple and areola are clearly seen and the breast bud

is up to 1.0 cm in diameter. In the rst weeks aer delivery,

the breast bud is visible and palpable; however, the gland then

regresses to a quiescent stage as maternal hormones in the

infant diminish. Aer this, the gland grows only in proportion

to the rest of the body until puberty.

PUBERTAL DEVELOPMENT

With the onset of puberty in the female, further growth of

the breast occurs, and the areolae enlarge and become more

pigmented. e further development of the breast involves two

distinct processes: organogenesis and milk production. e

ductal and lobular growth is organogenesis, and this is initiated

before and throughout puberty, resulting in the growth of breast

parenchyma with its surrounding fat pad. e formation of

alveolar buds begins within 1 to 2 years of the onset of menses

and continues for several years, producing alveolar lobes. is

menarchial stimulus begins with the extension of the ductal tree

and the generation of its branching pattern. e existing ducts

elongate. e ducts can develop bulbous terminal end buds that

are the forerunners of alveoli. e formation of the alveolar bud

begins within 1 to 2 years of the onset of menses. During this

ductal growth, the alveoli enlarge and the nipple and areola

become more pigmented. is growth involves an increase in

connective tissue, adipose tissue, and vascular channels and is

stimulated by estrogen and progesterone released by the ovary.

Stages of Mammary Development

Developmental Stage Hormonal Regulation Local Factors Description

Embryogenesis ? Fat pad necessary for

ductal extension

Epithelial bud develops in 18- to 19- week-

old fetus, extending short distance into

mammary fat pad with blind ducts that

become canalized; some milk secretion may

be present at birth

Mammogenesis Anatomic development

Puberty

Before onset of

menses

Estrogen, GH IGF- I, hGF, TGF- β;

others?

Ductal extension into mammary fat pad;

branching morphogenesis

After onset of

menses

Estrogen, progesterone; PRL? Lobular development with formation of

terminal duct lobular unit

Pregnancy Progesterone, PRL, hPL HER; others? Alveolus formation; partial cellular differentiation

Lactogenesis Progesterone withdrawal, PRL,

glucocorticoid

Not known Onset of milk secretion

Stage I: midpregnancy

Stage II: parturition

Lactation PRL, oxytocin FIL Ongoing milk secretion

Involution PRL withdrawal, alpha-

lactalbumin dimer

Milk stasis; FIL? Alveolar epithelium undergoes apoptosis and

remodeling; gland reverts to prepregnant

state

FIL, Feedback inhibition of lactation; GH, growth hormone; HER, heregulin; hGF, human growth factor; hPL, human placental lactogen; IGF- I,

insulin- like growth factor I; PRL, prolactin; TGF- β, transforming growth factor- β.

Modiﬁed from Neville MC. Mammary gland biology and lactation: a short course. Presented at: International Society for Research on Human Milk

and Lactation annual meeting; October 1997; Plymouth, MA.

TABLE

11.3

Adipose

stroma

Adipose

stroma

Te rminal

end bud

PRL

progesterone

GH,

estradiol

(IGF-I, HGF/SF,

TGF-β)

Ductal elongation

branching patterning

Epithelial

bud

Formation of

alveolar bud

(HER)

Figure 11.2 Schema for hormonal regulation of mammary development in the mouse. GH, Growth hormone; HER, heregulin; HGF/SF, human

growth factor/secretory factor; IGF- I, insulin- like growth factor I; PRL, prolactin; TGF- β, transforming growth factor- β. (From Neville MC. Mammary

gland biology and lactation: a short course. Presented at: International Society for Research on Human Milk and Lactation annual meeting; October

1997; Plymouth, MA.)

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11 The Breast and the Physiology of Lactation 169

During the menstrual cycle, there continues to be cyclic

microscopic proliferation and regression of ductal breast tissue.

e breast continues to enlarge slightly with further division of

the ductal system until about the age of 28 unless pregnancy

intervenes.

THE MATURE BREAST

e mature breast is located in the supercial fascia between

the second and sixth intercostal cartilages and is supercial to

the pectoralis muscle. It measures 10 to 12 cm in diameter. It

is located horizontally from the parasternal to the midaxillary

line. e central thickness of the gland is 5 to 7 cm. In the

nonpregnant state, the breast weighs on average 200 g. During

pregnancy, however, the size and weight increase to about 400 to

600 g, and to 600 to 800 g during lactation. Early in pregnancy

there is a signicant increase in ductal expansion and branching

attributed to estrogen. Lobular formation increases due to

prolactin, progesterone, and chorionic gonadotropin. By the

third month of gestation, secretory material like colostrum is

present in acini. Prolactin stimulates the secretion of colostrum

in the second trimester, but production of milk prior to delivery

is limited by the presence of progesterone. A projection of

mammary tissue into the axilla is known as the tail of Spence

and is connected to the central duct system. e breast is usually

dome shaped or conic, becoming more hemispheric in the adult

and pendulous in the older parous woman.

ABNORMALITIES

In some women, mammary tissue develops at other sites in the

galactic band. is is referred to as hypermastia, which is the

presence of accessory mammary glands that are phylogenic

remnants. ese remnants may include accessory nipples or

accessory gland tissue located anywhere along the milk line.

From 2% to 6% of women have hypermastia. ese remnants

remain quiet until pregnancy, when they may respond to the

hormonal milieu by enlarging and even secreting milk during

lactation. If le unstimulated, they will regress aer the birth.

Major glandular tissue in the axilla may pose a cosmetic or

management problem if the tissue enlarges signicantly during

pregnancy and lactation, secreting milk. It is distinct from the

tail of Spence.

Other abnormalities include amastia (absence of the breast

or nipple), amazia, hyperadenia, hypoplasia, polythelia, and

symmastia (Box 11.2). Abnormalities of the kidneys have been

associated with polythelia. Other variations include hyperplasia

or hypoplasia in various combinations, as listed in Box 11.3.

Gigantomastia is the excessive enlargement of the breasts

in pregnancy and lactation, sometimes to life- threatening

proportions. is enlargement may occur with the rst or any

pregnancy and may not recur. e enlargement recedes but

rarely back to original size.

Breastfeeding has been successful

in some cases of gigantomastia with appropriate professional

support. In extreme cases, gigantomastia may require heroic

measures, including emergency mastectomy.

Mothers with congenital abnormalities of the breast may

wish to breastfeed. Not all abnormalities or variations preclude

breastfeeding, and the decision is made on a case- by- case basis.

NIPPLE AND AREOLA

e skin of the breast includes the nipple and areola and the thin,

exible, elastic skin that covers the body of the breast. e nipple

is a conic elevation in the center of the areola at the level of about

the fourth intercostal space, just below the midline of the breast.

e nipple contains smooth muscle bers and is richly innervated

with sensory and pain bers. It has a verrucous surface and has

sebaceous and apocrine sweat glands but not hair.

e areola surrounds the nipple and is also slightly pigmented

and becomes deeply pigmented during pregnancy and lactation.

e average diameter is 15 to 16 mm, but the range may exceed

5 cm during pregnancy. e sensory innervation is less than that

of the nipple. e nipple and areola are very elastic and elongate

into a teat when drawn into the mouth by the suckling infant.

e surface of the areola contains Montgomery glands, which

hypertrophy during pregnancy and lactation and resemble

vesicles. During lactation, they secrete a sebaceous material to

lubricate the nipple and areola and protect the tissue while the

infant suckles. ese glands atrophy aer weaning and are not

visible to the naked eye except during pregnancy or lactation.

Each nipple contains 4 to 18 lactiferous ducts, of which 5 to

8 are main ducts surrounded by bromuscular tissue.

ese

ducts end as small orices at the tip of the nipple from which the

milk ows. e corpus mammae is an orderly conglomeration

of a number of independent glands known as lobes. e

morphology of the gland includes parenchyma that contains the

ductular- lobular- alveolar structures. It also includes the stroma,

which is composed of connective tissue, fat tissue, blood vessels,

nerves, and lymphatics.

Accessory breast: Any tissue outside the two major glands

Amastia: Congenital absence of breast or nipple

Amazia: Nipple without breast tissue

Hyperadenia: Mammary tissue without nipple

Hypoplasia: Underdevelopment of breast

Polythelia: Supernumerary nipple(s) (also hyperthelia)

Symmastia: Webbing between breasts

From Lawrence RA, Lawrence RM. Breastfeeding: A Guide for the

Medical Profession. 8th ed. St Louis, MO: Mosby; 2015:39.

BOX 11.2 BREAST ABNORMALITIES

HYPOPLASIA

Unilateral hypoplasia, contralateral breast normal

Unilateral hypoplasia, contralateral breast hyperplasia

Unilateral hypoplasia of breast, thorax, and pectoral muscles

(Poland syndrome)

Bilateral hypoplasia with asymmetry

HYPERPLASIA

Unilateral hyperplasia, contralateral breast normal

Bilateral hyperplasia with asymmetry

ACQUIRED ABNORMALITIES

Caused by trauma, burns, radiation treatment for hemangioma

or intrathoracic disease, chest tube insertion in infancy, and

preadolescent biopsy

From Lawrence RA, Lawrence RM. Breastfeeding: A Guide for the

Medical Profession. 8th ed. St Louis, MO: Mosby; 2015:40.

BOX 11.3 TYPES OF BREAST HYPOPLASIA,

HYPERPLASIA, AND ACQUIRED

ABNORMALITIES

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PART 1 Scientiﬁc Basis of Perinatal Biology

170

e mass of breast tissue consists of tubuloalveolar glands

embedded in adipose tissue, which gives the gland its smooth,

rounded contour. e mammary fat pad is essential for the

proliferation and dierentiation of the ductal arborization (Fig.

11.3). Each lobe is separated from the others by connective

tissue and opens into a duct that opens into the nipple. e

extension of ducts is orderly and protected by an inhibitory

zone into which other ducts cannot penetrate.

Blood is supplied to the breast from branches of the

intercostal arteries and perforating branches of the internal

thoracic artery. e main blood supply comes from the internal

mammary artery and the lateral thoracic artery. e venous

supply parallels the arterial supply.

Lymphatic drainage has been thoroughly studied by

researchers of breast cancer. e main drainage is to axillary

nodes and the parasternal nodes along the thoracic artery

within the thorax. e lymphatics of the breast originate in

lymph capillaries of the mammary connective tissue and drain

through the deep substance of the breast.

e breast is innervated from the branches of the fourth,

h, and sixth intercostal nerves. e sensory innervation of

the nipple and areola is extensive and includes both autonomic

and sensory nerves. e innervation of the corpus mammae

is meager by comparison and is predominantly autonomic.

Neither parasympathetic nor cholinergic bers supply any part

of the breast. e eerent nerves are sympathetic adrenergic.

Most of the mammary nerves follow the arteries. A few bers

course along the walls of the ducts. ey may be sensory bers

that sense milk pressure. No innervation has been identied to

supply the myoepithelial cells. e conclusion is that secretory

activities of the acinar epithelium of the ducts depend on

hormonal stimulation, such as by oxytocin.

When sensory bers are stimulated, the release of

adenohypophyseal prolactin and neurohypophyseal oxytocin

occurs. e areola is most sensitive to the stimulus of suckling

and the nipple the least; the skin of the breast is intermediate.

e large number of dermal nerve endings results in high

responsiveness to suckling. Pain bers are more numerous in the

nipple, with few in the areola. All cutaneous nerves run radially

toward the nipple. Breast nerves can inuence the mammary

blood supply and therefore also inuence the transport of

oxytocin and prolactin to the myoepithelial cells and the lacteal

cells, respectively.

MAMMARY GLAND IN PREGNANCY

During the rst trimester, rapid growth and branching from the

terminal duct system into the adipose tissue is stimulated by the

changing levels of circulating hormones. As epithelial structures

proliferate, adipose tissue decreases. ere is increased

inltration of the interstitial tissue with lymphatics, plasma

cells, and eosinophils. By the third trimester, parenchymal

cell growth slows and alveoli become distended with early

colostrum. Alveolar proliferation is extensive.

e lactating mammary gland has many alveoli that are

made up of cuboidal, epithelial, and myoepithelial cells. Little

connective tissue separates the alveoli. Lipid droplets are visible

in the cells. By complex interplay of the nervous system and

endocrine factors (progesterone, estrogen, thyroid, insulin,

and growth factors), the mammary gland begins to function

(lactogenesis stage I) and other hormones establish the milk

secretion and maintain it (lactogenesis stage II).

Human prolactin has a signicant role in both pregnancy

and lactation. e levels are high during pregnancy, but the

inuence of prolactin on the breast itself is inhibited by a

hormone produced by the placenta, originally referred to as

prolactin- inhibiting hormone but believed to be progesterone.

Physiology of Lactation

LACTOGENESIS

Lactation is the physiologic completion of the reproductive

cycle. e human infant is the most immature and dependent

of all mammals except for marsupials, and thus the breast

provides the most physiologically appropriate nutrients

required by the human infant at birth. roughout pregnancy,

the breast develops and prepares to take over the role of fully

nourishing the infant when the placenta is expelled. e breast

is prepared for full lactation aer 16 weeks’ gestation. e

physiologic adaptation of the mammary gland to its role in

infant survival is a complex process, only the outline of which

is discussed here. ere are a number of complete reviews of

the newer scientic studies on the physiology of lactation.

89- 91

Hormonal control of lactation can be described in relationship

to the ve major changes in the development of the mammary

gland: embryogenesis, mammogenesis or mammary growth,

lactogenesis or initiation of milk secretion, lactation or full milk

secretion, and involution (see Table 11.3). Detailed explanation

of mammary growth is beyond the scope of this discussion. e

two most important hormones involved in lactation itself are

prolactin and oxytocin, and these are described with respect to

their impact on lactogenesis.

Lactogenesis is the initiation of milk secretion, beginning

with the changes in the mammary epithelium in early pregnancy

and progressing to full lactation. Stage I lactogenesis occurs

Mammary

lobus containing

several lobuli

Mammary

lobulus containing

10 to 100 alveoli

Areola

mammae

Montgomery

glands

Mammary

fat

Connective

tissue septa

Figure 11.3 Morphology of the mature breast. Diagrammatic dis-

section reveals mammary fat and duct system. (Modiﬁed from Lawrence

RA, Lawrence RM. Breastfeeding: A Guide for the Medical Profession.

9th ed. St Louis, MO: Mosby; 2021:45.)

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11 The Breast and the Physiology of Lactation 171

during pregnancy and is achieved when the gland is suciently

dierentiated to secrete milk. It is prevented from doing so by

high circulating plasma concentrations of progesterone.

Stage

II is the onset of copious milk secretion associated with delivery

of infant and the placenta.

e progesterone level decreases

sharply, by 10- fold in the rst 4 days. is is accompanied by

the programmed transformation of the mammary epithelium.

By day 5, the infant has 500 to 750 mL of milk available (Fig.

11.4). e changes in milk composition that occur in the rst

10 postpartum days should be viewed as part of a continuum in

which the rapid changes of the rst 4 days are followed by slower

changes in various components of milk throughout lactation.

A change in permeability of the paracellular pathways results

in a shi from high concentrations of sodium, chloride, and

the protective immunoglobulins and lactoferrin, little lactose,

and no casein in colostrum to increasing amounts of all milk

components.

Lactogenesis stage II results in an increase of milk from 100

mL in the rst 24 hours to large volumes (500 to 750 mL/day)

by day 4 or 5, gradually leveling o at 600 to 700 mL/day by

day 8.

ese volume changes are associated with a decrease in

sodium and chloride concentration and an increase in lactose

concentration. e production of lactose drives the production

of milk. e early changes in sodium and chloride are a function

of the closure of the tight junctions that block the paracellular

pathway.

96- 98

Secretory IgA and lactoferrin represent 10% by

weight of the milk produced in the rst 48 hours, and although

their amounts remain the same, the increased volume of milk

produced decreases their concentration. At 8 days, secretory

IgA and lactoferrin are 1% by weight and 2 to 3 g/day.

At 36 postpartum hours (in multiparas) and at up to 72

hours (in primiparas), milk production increases 10- fold (from

50 to 500 mL/day). Women refer to this as their milk “coming

in.” It reects a massive increase in synthesis and secretion of

the components of mature milk, including lactose, protein, and

lipid.

During pregnancy, hormones maintain the pregnancy and

produce mammary tissue that is prepared to produce milk but

does not do so. Progesterone, prolactin, and possibly placental

lactogen are credited with the development of the alveoli.

Progesterone has been identied as the major inhibitor of milk

production during pregnancy.

100

Prolactin levels in pregnancy

are greater than 200 ng/mL. Apparently, the continued high

level of prolactin and a decrease in progesterone are necessary

for stage II lactogenesis aer parturition.

100

e placenta is

the main source of progesterone in pregnancy. Aer the birth,

progesterone receptors are lost in the human breast and estrogen

levels drop precipitously.

In addition to prolactin, insulin and corticoids are essential

to milk synthesis.

101

Delayed lactogenesis is seen in women who

had retained placenta, cesarean section, diabetes, and stress

during delivery.

95,101- 103

Many factors contribute to delayed

onset of lactogenesis in women with gestational diabetes,

including prepregnancy obesity, older maternal age, and

insulin requirement for gestational diabetes.

104- 106

In the 1940s,

Jackson rst noted that stressful labors inuenced the early

breastfeeding experience in the rooming- in unit.

107

Stress alone

may be the trigger for delayed lactogenesis in the conditions

other than retained placenta.

83,108

It has been observed that

high sodium levels in early milk samples are seen in pregnancy,

mastitis, involution (weaning), premature birth, and inhibition

of prolactin secretion by bromocriptine. ese observations

suggest that junctional closure depends on adequate suckling

or eective milk removal in the rst 3 postpartum days. e

signicance of having a high sodium concentration in breast

milk requires further study.

If milk removal does not begin by 72 hours, the changes in

milk composition associated with lactogenesis are reversed and

the probability that lactation will be successful decreases.

109

us clinical eorts that facilitate early suckling by the newborn

enhance the probability of lactation success. Early stimulation of

the breast by pumping before 72 postpartum hours is essential

when the infant is unable to nurse directly. Initiation of milk

expression within the rst 6 hours aer birth has resulted in

increased milk volume, greater colostrum production, and

sustained milk volumes.

110

is knowledge is important to

reinforce with mothers, families, and sta to encourage and

facilitate early expression of milk by mothers of premature

infants or when infants and mothers are separated for any

reason.

LET- DOWN (EJECTION) REFLEX

An eective let- down reex is key to successful lactation. is

reex, also known as the ejection reex, was rst described

in humans by Peterson and Ludwick in 1942

111

and was later

demonstrated clinically by Newton and Newton to be caused by

the release of oxytocin by the pituitary.

Since that time, many

renements in the understanding of the process of milk ejection

have been published,

112- 114

but the fundamental principles are

unchanged (Fig. 11.5). A mother may produce milk, but if it is

not excreted, further production is eventually suppressed. e

reex is a complex function that depends on hormones, nerves,

and glandular response and can be inhibited most easily by

psychological inuences.

Oxytocin is the hormone responsible for stimulating the

myoepithelial cells to contract and eject the milk from the ductal

system. e ducts begin at the alveoli, which are surrounded by

a basket- like structure of myoepithelial cells that also surround

the ducts all the way to the nipple. When the infant stimulates

the breast by suckling, impulses sent to the central nervous

system and to the posterior pituitary result in the release of

oxytocin, which is then carried by the bloodstream to the

800

600

mL/day

400

200

02 46 8

Postpartum day

Figure 11.4 Milk volumes during ﬁrst postpartum week. Mean val-

ues from 12 multiparous White women who test- weighed their infants

before and after every feeding for the ﬁrst 7 postpartum days. (Redrawn

from Neville MC, Keller RP, Seacat J, et al. Studies in human lactation:

milk volumes in lactating women during the onset of lactation and full

lactation. Am J Clin Nutr. 1988;48:1375–1386.)

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PART 1 Scientiﬁc Basis of Perinatal Biology

172

myoepithelial cells. is is a neuroendocrine reex. Oxytocin

release can also be stimulated by other pathways of sight, sound,

and smell that represent the infant. Oxytocin also stimulates

the myoepithelial cells in the uterus, which are very sensitive

to oxytocin during parturition and for a week or so aer the

birth. is causes the uterus to contract, decreases blood loss,

and hastens postpartum involution. e uterus of a mother who

breastfeeds returns to a prepregnant state more rapidly. e

uterine cramping experienced while breastfeeding is a result of

this stimulus (see Fig. 11.6).

Newton and Newton

demonstrated that pain and stress

interfered with the let- down reex because it interfered with

oxytocin release. In their experimental model, they stimulated

stress with pain, loud noises, or pressure to solve mathematical

problems. In other species, oxytocin release has been shown to

stimulate mothering behaviors.

115

Levels of adrenocorticotropin

and plasma cortisol are decreased in lactating women compared

with nonlactating women in response to stress.

Prolactin is central to the production of milk and regulates

the rate of synthesis. Its release depends on the suckling of the

Afferent arcs

Suckling

Oxytocin

Prolactin

Direct

reflex arc

Cervical

dilation

Hypothalamus

Prolactin-inhibiting factor

Pituitary

Figure 11.5 Neuroendocrine control of milk ejection. (Modiﬁed from Vorherr H. The Breast: Morphology, Physiology and Lactation. New York,

NY: Academic Press; 1974.)

Oxytocin

Uterus

Pituitary gland

Myoepithelial

cell

Lacteal cell

Prolactin

Hypothalamus

Figure 11.6 Diagram of let- down (ejection) reﬂex arc. When the infant suckles the breast, mechanoreceptors in the nipple and areola are stimu-

lated, which sends a stimulus along nerve pathways to the hypothalamus, which stimulates the posterior pituitary gland to release oxytocin. Oxytocin

is carried via the bloodstream to the breast and uterus. Oxytocin stimulates myoepithelial cells in the breast to contract and eject milk from the alveo-

lus. Prolactin is responsible for milk production in the lacteal cells lining the alveolus. Prolactin is secreted by the anterior pituitary gland in response

to suckling. Stress (e.g., pain, anxiety) can inhibit the let- down reﬂex. Seeing or hearing the cry of the infant can stimulate the release of oxytocin but

not prolactin. (From Lawrence RA, Lawrence RM. Breastfeeding: A Guide for the Medical Profession. 7th ed. St Louis, MO: Mosby; 2010:259.)

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11 The Breast and the Physiology of Lactation 173

infant or the stimulation of the nipple by mechanical pumping

or manual expression. Prolactin is also released through a

neuroendocrine reex. Its inuence is modied, however,

by the actual release of milk from the alveoli. Local factors in

the ductal system or in the accumulated milk can inhibit milk

release and thus inhibit further milk production. Prolactin is

not released as a result of sound, sight, or smell of the infant, as

is the case with oxytocin, but only by suckling (Fig. 11.7).

INITIATION OF LACTATION

Although breastfeeding is a natural process in postpartum

women, it is a learned skill, not a reex. Because the incidence

of breastfeeding in developed countries dropped to about

10% in the 1950s and 1960s, there are few experienced role

models available to support, encourage, and assist new mothers

in feeding their infants at the breast. In the late 1940s, Edith

Jackson at Yale, in cooperation with Herbert oms, established

the rst rooming- in unit in the United States, introduced

“childbirth without fear,” and reestablished breastfeeding as

the norm for mothers and infants at the Yale New Haven

Hospital.

116

Obstetric and pediatric residents were well schooled

in the practical aspects of breastfeeding and human lactation.

Jackson and her pediatric colleagues published the classic article

on the management of breastfeeding,

117

on which decades of

publications, both lay and professional, were based.

e obstetrician and pediatrician have become more involved

in the decision to breastfeed and in the practical management of

the mother- infant dyad. Medical schools are gradually adding

breastfeeding and lactation to their curriculum. Although it is not

the physician’s role to put the infant to the breast, it is important

to understand the process, to recognize problems, and to know

how to solve them. Breastfeeding support is a team eort in

which the physician works with many health care professionals,

including nurses, midwives, doulas, and dietitians, to provide

complete care to the perinatal patient. Lactation specialists

may be nurses, dietitians, nonmedical individuals with special

training, or physicians with specialty designation. e physician

should be sure that consultants are licensed and board certied

by the International Board of Lactation Consultant Examiners

and that other collaborating physicians are recognized as fellows

of the Academy of Breastfeeding Medicine.

Except in extreme cases, breast size does not inuence milk

production. Augmentation mammoplasty does not interfere

with lactation unless a periareolar incision was made and

nerves were interrupted. If augmentation was done for cosmetic

enhancement, the tissue should function well, but if there was

little or no palpable breast tissue before surgery, lactation may

be improbable.

Reduction mammoplasty is more invasive surgery, and

lactation results depend on the technique used. If many ducts

were severed and the nipple and areola transplanted, lactation

is interfered with. However, if the nipple and areola remained

intact on a pedicle of ducts, lactation could be successful. Other

incisions (e.g., for lump removal) should be discussed but

usually do not interfere with lactation.

During pregnancy, the obstetrician should document the

changes in the breasts in response to pregnancy, when the

nipple and areola should become more pigmented and enlarged

and the breast should enlarge one- half cup size or more. Lack of

breast changes should also be communicated to the pediatrician,

because this represents a risk for early failure to thrive in the

infant because of insucient milk supply. A breast examination

should be conducted late in the pregnancy to check for any new

ndings of masses, lumps, discharge, or pain. Berens described

the role of the obstetrician throughout pregnancy in detail.

118

Initiating Breastfeeding

e ideal time to initiate breastfeeding is immediately aer birth

(the Baby- Friendly Initiative recommends within 1 hour of birth).

When le on the mother’s abdomen to explore, the unmedicated

newborn will move toward the breast, latch on, and begin suckling.

is usually takes 20 to 30 minutes if unassisted.

119

is has been

described as initiating breastfeeding by breast crawl.

120

e infant

is ready to feed and has been sucking in utero since about 14 weeks’

gestation, consuming amniotic uid daily (about 1 g protein/kg

of fetal weight is received daily from amniotic uid). e infant

at 28 weeks’ gestation has already developed coordinated rooting,

suckling, and swallowing necessary for breastfeeding. e ability to

coordinate suck and swallow while bottle feeding does not occur

until 34 weeks.

Holmes and coworkers outlined recommendations for

peripartum breastfeeding management for the healthy mother

and infant at term.

121

Shortly aer delivery, the mother should

be oered the opportunity to breastfeed and should be assisted

to assume a comfortable position, usually lying on her side. e

infant can be placed beside her, tummy to tummy, facing the

breast. e mother should support her breast with her hand,

keeping her ngers behind the areola so the infant can latch

on. e mother should stroke the center of the infant’s lower

lip with the breast (see Fig. 11.8).

122

e infant should open the

mouth wide, extend the tongue, and draw the nipple and areola

into the mouth to form a teat. e teat is compressed against the

palate by the tongue, and the gums and lips form a seal with the

60 30 030

100

200

300

400

500

1000

2000

Play with

Infant

Milk

Let-

Down

Nursing

60 90

Time in minutes

120 150

Prolactin ng/mL

180

Figure 11.7 Plasma prolactin stimulation. Plasma prolactin levels

were measured by radioimmunoassay before, during, and after a period

of nursing in three mothers between 22 and 26 days after the birth. The

levels rose with suckling but not with infant contact only. (Modiﬁed from

Josimovich JB, Reynolds M, Cobo E. Lactogenic hormones, fetal nutri-

tion, and lactation. In: Josimovich JB, Reynolds M, Cobo E, eds. Prob-

lems of Human Reproduction. Vol 2. New York, NY: John Wiley & Sons;

1974:1.)

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PART 1 Scientiﬁc Basis of Perinatal Biology

174

breast. It is the peristaltic motion of the tongue that stimulates

the let- down reex. e continued peristaltic motion travels

to the posterior tongue, the pharynx, and down the esophagus

as one coordinated motion so that swallowing is automatically

coordinated with suckling during breastfeeding.

Ultrasound imaging of milk ejection in the breasts of

lactating women has provided a more detailed description

of the process compared with the traditional serial sampling

of plasma oxytocin levels and measurements of intraductal

pressure. A signicant increase in milk- duct diameter can be

observed during milk ejection. Multiple milk ejections occur

during the process and are correlated with milk ow and with

the changes in milk- duct diameter, although they are not sensed

by the mother.

114,123

e number of milk ejections inuences

the amount of milk available to the infant.

Sucking an articial nipple is a quite dierent tongue motion

that is not coordinated with swallow. A newborn should

not be given a bottle to test his or her feeding ability before

breastfeeding. It is wise to avoid all articial nipples (bottles

or paciers) in the early weeks of breastfeeding. If, for medical

reasons, the infant requires donor human milk or a breast milk

substitute, it can be given by medicine cup (cup feeding), spoon,

dropper, or supplemental feeder.

124- 126

e initial contact may be limited to exploration of the

breast by the infant, with licking and nuzzling of the nipple,

or the infant may latch on and suck for minutes. Timing is not

necessary because the infant will interrupt him- or herself. In

the rst hour aer birth, the term unmedicated infant will be

quietly alert. It is an opportunity for the mother, father/partner,

and infant to get acquainted.

Ideally, mother and infant recover in the same room together.

e infant is fed on awakening, and the mother learns the early

signs of hunger. Crying is a late sign of hunger in the infant.

e mother also learns about caring for her healthy term infant.

ere should be no schedules and no intervention unless an

infant does not feed for over 6 hours. A normal feeding pattern

for breastfeeding in early infancy is 8 to 12 feeds every 24 hours

until satiety. e nursing sta and lactation consultants ensure

that the infant latches on well and the mother’s questions are

answered. Breastfeeding should not hurt; when it does, the

process should be observed and adjusted. e obstetrician

should be involved if needed in the evaluation of breast pain and

can review frequent and eective feeding prior to the mother’s

discharge. e physician should observe a feeding as part of

the infant’s discharge examination. If there is persistent breast

or nipple pain with breastfeeding additional evaluation will be

needed as outlined by the Academy of Breastfeeding Medicine’s

Clinical Protocol #26: Persistent Pain with Breastfeeding or

ACOG Committee #820 on Breastfeeding Challenges.

127

e

mother should be aware of the milk letting down by tingling

in the breast or dripping from the opposite breast. During the

feeding session the infant should be observed in coordinated

sucking, swallowing, and breathing to eect adequate milk

transfer while breastfeeding. Breastfeeding infants use primarily

negative pressure to remove milk from the breast. Vacuum is

created by the downward movement of the anterior portion of

the tongue parallel to the hard palate. e infant does not suck-

swallow- breathe in a 1:1:1 ratio but in variable combinations of

the three actions during breastfeeding.

128

e infant’s weight is measured daily and again just before

discharge. A weight loss of greater than 5% in the rst 48

hours should be assessed by checking the feeding process

and reviewing voidings and stoolings. Maximum weight loss

should not exceed 7% in a breastfed infant by 72 hours. e

weight should plateau aer 72 to 96 hours and start to rise with

adequate feedings. Birth weight should be regained by 7 days

or, at the latest, 10 days by a breastfeeding infant. Flaherman

and colleagues have developed nomograms to track such weight

loss aer vaginal or cesarean births. ere is also an online tool

for calculating percent weight loss over time since birth at Penn

State Health, e NEWT Newborn Weight Tool.

129,130

A healthy infant voids at least once and stools at least once

in the rst 24 hours, both at least twice in the second 24 hours,

and both at least three times in the third 24 hours. From then on

voiding should occur at least six times daily. An infant should

stool at least once (and preferably three times) every day in the

rst month of life. Aer 3 to 4 months of age, a perfectly healthy

breastfed infant may go a week without stooling and then pass

a so yellow stool, but this should not occur under 1 month of

age.

Early discharge from the hospital has increased the need for

newborn care visits within a few days aer discharge and as

required thereaer at 2- to 4- week intervals for assessment. A

follow- up visit at 48 to 72 hours aer discharge, or at 3 to 5 days

of age for infants discharged at 48 hours or less, is recommended

for reassessment of latch, ecacy of feeding, feeding pattern(8

Figure 11.8 Getting a good latch. (a) Tickle the baby’s lips with your nipple to encourage him or her to open wide, (b) pull your baby close so

that the baby’s chin and lower jaw move in to your breast, and (c) watch the baby’s lower lip and aim it as far from the base of the nipple as possible

so that the baby takes a large mouthful of breast. (From Ofﬁce on Women’s Health in the US Department of Health and Human Services. Getting a

Good Latch. https://www.womenshealth.gov/breastfeeding/learning- breastfeed/getting- good- latch. Updated August 28, 2018. Accessed January

30, 2021.)

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11 The Breast and the Physiology of Lactation 175

to 12 feeds every 24 hours), hydration status, and frequency of

urination and stooling.

6,8

e transition from hospital to home is a stressful time for all

families, but when an infant is premature, small for gestational

age, or even near term, transition can be extremely dicult.

e stress can be reduced by appropriate detailed discharge

planning. e presence of eective, coordinated sucking,

swallowing, and breathing should be pointed out to the parents

and documented in the chart. Mothers/parents should receive

adequate assistance in the days before discharge; positioning,

latch, and milk transfer should be perfected, or gavage feeding,

supplementation, and fortication should be managed by the

parents prior to discharge. e AAP Committee on Fetus and

Newborn has delineated the following three competencies of

infants that are recognized as essential before hospital discharge

of the preterm infant: the ability to maintain body temperature

in a home environment, suciently mature respiratory control,

and oral feeding with or without gavage feeding sucient to

support appropriate growth.

131,132

Issues in the Postpartum Period

BREAST ENGORGEMENT AND NIPPLE

TENDERNESS

A little engorgement of the breast in the rst 24 hours is

physiologically normal as the vascular supply shis from the

once- gravid uterus to the breasts. Absence of any engorgement,

such as absence of breast growth during pregnancy, is cause

for concern. Not only is excess engorgement painful but the

increased vascular pressure compresses the alveoli and ducts

and interferes with milk production and release.

74,133

Prevention

of excessive engorgement is the best treatment and involves the

following: (1) wearing a well- tting nursing brassiere, even

before the breasts are engorged, and around the clock; (2)

frequent feedings for the infant, being sure to balance the use

of both breasts; (3) gentle massage and soening of the areola

before oering the breast to the infant, so that proper latch- on

can be accomplished; (4) if necessary, applying cold packs or

cold compresses aer a feeding; and (5) taking acetaminophen

or ibuprofen, which may be safely used by the mother for

discomfort. erapeutic breast massage during lactation is a

recently studied intervention that is being recommended.

134

Peak engorgement usually occurs between 72 and 96

postpartum hours when the mother has arrived home and is on

her own. At the peak of discomfort, standing in a warm shower

to let milk drip or applying warm compresses before pumping

to relieve the pressure and stimulate ow provides relief before

the phenomenon subsides. Although a variety of remedies

have been recommended for engorgement, there is insucient

published evidence to recommend one individual treatment

over others.

135- 137

Sore nipples are a common complaint when early lactation

has gone unassisted. It should not hurt to breastfeed. When it

does hurt, the infant should be taken o the breast by breaking

the suction with a nger and reattaching the infant carefully,

following the steps previously described. e major cause of sore

nipples is inadequate latch- on. It is not caused by breastfeeding

too long or too frequently. A newborn usually feeds about every

2 hours in the rst few weeks of life. Persistent sore nipples,

cracks, or oozing may require the assistance of a licensed certied

lactation consultant or breastfeeding medicine specialist who

can take the time and has the experience to work with the

mother to identify the cause, determine eective treatment, and

assist the dyad in maintaining pain- free breastfeeding.

127,138

A clinically dened phenomenon has recently been described

in which breastfeeding mothers become acutely saddened,

tearful, and depressed with milk ejection. is picture has been

described as a dysphoric milk- ejection reex (D- MER). A clinical

case study and a descriptive study by Ureno and colleagues have

related this picture to a severe drop in maternal dopamine and

described ameliorating factors including distraction, chocolate

ice cream, herbals, smoking cigarettes, pseudoephedrine, and

bupropion.

139,140

Management of this condition should begin

with “normalization,” as the experience is oen accompanied

by signicant maternal guilt for feeling negatively toward the

supposedly positive experience of bonding, and can include

various distraction interventions. e physician should assist

the mother in deciding whether continued breastfeeding or

weaning is best for her and her child.

FAILING MILK SUPPLY

Many misconceptions lead to the impression that a failing milk

supply is a common occurrence. Many women discontinue

breastfeeding before 3 postpartum months, believing their milk

is diminishing because their breasts are no longer engorged. A

very common question for all breastfeeding mothers is “Am I

making enough milk?” ere is a legitimate question regarding

whether this is just the mother’s perception or actual insucient

milk production for appropriate infant growth.

141

Once supply

and demand have equilibrated and the breast makes what the

infant needs, the breasts are so and do not constantly drip. e

emptying time of the stomach of the infant fed human milk is

90 minutes, that of the infant fed formula is 3 to 4 hours, and

that of the infant fed cow’s milk is 6 hours. Continuing to feed

every 3 hours is a testimony to the breast milk’s digestibility, not

its inadequacy. Weight gain in the infant is the better barometer

of success. ACOG and AAP recommend that exclusive

breastfeeding should continue for 6 months, with continued

breastfeeding while adding weaning foods for the next 6 months

and then as long thereaer as mutually desired by mother and

child.

74,142

Genuine failure to produce enough milk may result from

infant causes, such as increased need, increased uid losses,

or lack of adequate suckling, or from maternal causes, such as

failure to let down or failure of production. Each case should be

carefully reviewed because most situations are remediable. ere

is a long list of conditions associated with low or insucient milk

supply in ACOG’s Committee Opinion #820 on Breastfeeding

Challenges.

Ideally, both the obstetrician and the pediatrician

are experienced in lactation management or have a sta member

who is. Working together with a licensed certied lactation

consultant, the issues can be resolved, and breastfeeding can

continue successfully. ere are common situations where the

evaluation of breastfeeding is appropriate but supplementation

with breast milk substitutes is not. Donor human milk should

be considered if it is available. ere are few situations when

supplementation in healthy term infants is indicated, and

some examples include asymptomatic hypoglycemia, signs

and symptoms indicative of inadequate milk intake (especially

infant weight loss or insucient gain), hyperbilirubinemia,

or the infant is ill, necessitating select macronutrients. Some

maternal indications for supplementation may include delayed

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PART 1 Scientiﬁc Basis of Perinatal Biology

176

secretory activation (with inadequate intake by the infant),

primary glandular insuciency, breast pathology or previous

surgery resulting in poor milk production, situations requiring

temporary cessation of breastfeeding (maternal chemotherapy),

and intolerable breast pain during feedings unimproved by

interventions.

143

In certain situations, galactogogues may be

recommended to maintain the milk supply. Published reviews

of the use of galactogogues are available.

144- 148

BREASTFEEDING AFTER PREMATURE OR

MULTIPLE BIRTHS

Human milk is benecial in the management of the premature

infant, according to the policy statement of the AAP.

is can be

mother’s own milk (MOM) or donor human milk (DHM).

149,150

e benets include infection protection; improvement

in gastrointestinal function, digestion, and absorption of

nutrients; and improvement in neurodevelopmental outcome.

e psychological well- being of the mother is enhanced when

she provides her milk for her compromised infant.

151

Meeting

the intrauterine rates of growth and nutrient accretion requires

attention. Although human milk satises these needs for larger

premature infants, it can be carefully supplemented for smaller

infants and still preserve the benets of human milk. Factors

related to the infants, the mothers, and clinical practice clearly

aect exclusive breastfeeding of premature infants.

152- 155

ere is

a commercial product created with 100% human milk developed

to enhance mother’s milk and replace supplementation made

with cow’s milk.

156

Twins and triplets present problems of time management for

the mother.

157

e mother will make enough milk, as supply will

meet demand. Twins learn quickly to nurse simultaneously and

will continue to do so for months or years. Breastfeeding ensures

a mother’s interaction with her infants. Helpful friends and

relatives can perform the other household duties. e mother

can also provide enough milk for triplets. Some mothers prefer

to nurse two at a feeding, giving the third a bottle but rotating

the three, feeding by feeding. Any breast milk is valuable in

this situation. Mothers of singleton infants may need help, but

mothers of multiples especially need help. It may be necessary

for the physician to prescribe help and careful attention to

proper rest. Mothers have also breastfed quadruplets and higher

numbers of infants. e mother can nurse several infants at

each feeding and rotate bottle feeding. Exclusive breastfeeding

of quadruplets for the rst year has been reported by Berlin.

158

Contraception

Open- ended questioning is appropriate to support maternal and

familial decision making about breastfeeding, sexuality, birth

spacing, and contraception. Appropriate information sharing

should include (1) there are improved maternal and infant

outcomes in subsequent pregnancies if the interpregnancy

interval is greater than 18 months, (2) exclusive and frequent

breastfeeding can be highly eective in birth spacing, and

(3) there are a number of options for contraception which

are both eective and safe during breastfeeding.

159

e

Centers for Disease Control and Prevention (CDC) and

WHO Medical Eligibility Criteria for Contraception include

the lactational amenorrhea method for birth spacing. e

published risk of pregnancy is less than 2% when women

meet three situational variables: amenorrhea, fully or nearly

fully breastfeeding with frequent feedings and no periods of

>4–6 hours between breastfeeds, and less than 6 months since

the most recent delivery.

160,161

Women should be aware that

these variables need to be met to provide protection against

pregnancy. Hormonal methods of contraception are oered

over nonhormonal/barrier methods due to their higher ecacy.

Estrogen or combination products are usually avoided before

6 weeks postpartum. Progestin- only contraceptives, such as

the mini- pill tablet, injectable medroxyprogesterone acetate

(Depo- Provera), and levonorgestrel implants, are the hormonal

methods of choice in this period. ere remain theoretical

concerns regarding whether exogenous progesterone disrupts

milk synthesis; however, some limited studies present data

that progestin- only methods are safe even in the rst 6 weeks

postpartum. is theoretical risk of diminished breastfeeding

with immediate postpartum progestin- only contraception

should be communicated to mothers and families to promote

and support autonomous informed decision making.

162

Recommendations for addressing contraception during

lactation are available from the Academy of Breastfeeding

Medicine and from ACOG.

163,164

ACOG maintains an online

resource for patients as well.

165

Maternal Infections During

Breastfeeding

Although oen a mother is concerned about the risk to a

breastfeeding infant when she has an infectious illness, maternal

infection is not a contraindication to breastfeeding in most

cases. Proscribing breastfeeding out of fear of infection deprives

infants of signicant immunologic, nutritional, and emotional

benets of breastfeeding when they are most needed.

e decision- making process to breastfeed despite maternal

infection should involve discussion of the usual route of

infection transmission, reasonable infection control precautions,

potential severity of infection in the infant or child, medications

to treat the mother that are compatible with breastfeeding, the

potential of prophylaxis for the infant, the protective eect of

breast milk, and the acceptability of using expressed breast milk

temporarily. e discussion should involve the mother and

family, weighing the known and potential risks of the infection

against the known benets of breastfeeding.

For example, diphtheria and active pulmonary tuberculosis

in the mother are commonly transmitted via the respiratory

route, so contact between infant and mother should be

proscribed regardless of how the infant is being fed. Diphtheria

and tuberculosis are not transmitted in the milk, except in the

case of cutaneous diphtheria involving the nipple and breast

or tuberculosis mastitis. As long as there are no lesions on the

breast, expressed breast milk can be given to the infant during the

initial treatment of the mother (probable infectious periods are

5 days for diphtheria and 14 days or until the sputum is negative

for acid- fast tuberculous bacilli). Prophylactic antibiotics for the

infant are appropriate in each case—penicillin or erythromycin

for diphtheria and isoniazid for tuberculosis.

9,166,167

Brucellosis is known to be transmitted via unpasteurized

milk of animals. ere are case reports of transmission of

brucella from mothers to infants via breast milk, but human-

to- human transmission is rare overall. In the case of suspected

maternal brucellosis, rst conrm the diagnosis by culture and

serology and then treat the mother during pregnancy between

12 and 36 weeks of gestation with rifampicin and trimethoprim/

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11 The Breast and the Physiology of Lactation 177

sulfamethoxazole to avoid disrupting organogenesis prior to 12

weeks or causing neonatal kernicterus aer 36 weeks. If the

mother has been eectively treated the infant can breastfeed,

or the infant can be given rifampicin beginning at birth with

trimethoprim/sulfamethoxazole added aer 4 weeks of age as

prophylaxis while continuing breastfeeding.

168

In certain highly contagious and serious infections such as

the hemorrhagic fevers—specically with Ebola, Marburg, or

Lassa virus—the risk of transmission from any contact with the

infected mother is high. e CDC and WHO recommend that, if

there are safe alternatives to breastfeeding and care of the infant

by another unexposed, uninfected adult, then mothers with

probable or conrmed Ebola virus disease should be separated

from the infant until recovery.

169,170

A safe, feasible alternative

source of feeding is essential before considering withholding

breast milk. If feasible, pasteurized mother’s milk (via routine

pasteurization, Pretoria pasteurization, or ash heating) may be

utilized in special circumstances when alternative feeding is not

available.

170,171

ere have been few case reports on transmission of dengue

virus or other aviviruses to infants via breast milk. It has been

recommended to suspend breastfeeding once the diagnosis is

made in a mother, maintain the milk supply by pumping and

discarding the milk, and reinitiate breastfeeding when the

mother is well. is may not be feasible if an alternative source

of infant feeding is not available.

172,173

Possible West Nile virus (WNV) transmission to an infant

through breastfeeding has been reported,

174

but the data on this

infection in pregnant or breastfeeding women and their infants

are limited. Hinckley and coworkers reported 10 instances of

maternal or infant WNV- related illness while breastfeeding. In

ve cases, the transmission of WNV through breast milk could

not be conrmed or ruled out, and in the other ve cases, there

was no evidence of vertical transmission. ey concluded that

the information they presented does not support a change in

breastfeeding practices aer infection with WNV, and that more

information is needed.

175

In the case of infections at specic sites in the mother, the

management varies with the specic etiologic organism. For

example, with mastitis, continued eective milk removal

is the essential rst step along with supportive measures

(rest, adequate uids and nutrition, and breast massage) and

analgesia. If the obstruction to milk ow and inammation

progress in the next 24 hours, antibiotics are indicated. Empiric

antibiotics for acute lactational infectious mastitis include

dicloxacillin, ucloxacillin, or a rst- generation cephalosporin.

For methicillin- resistant Staphylococcus aureus coverage,

local resistance patterns should be reviewed; clindamycin,

trimethoprim/sulfamethoxazole, or vancomycin are options.

Alternative therapy for penicillin allergy includes erythromycin,

clindamycin, or trimethoprim/sulfamethoxazole. Close follow-

up for improvement of symptoms and for potential abscess

formation are appropriate. Physical exam should be adequate

to diagnose an abscess, but an ultrasound can help on occasion

and can guide aspiration/drainage.

176

Cytomegalovirus

(CMV) is transmitted from the mother to the infant via breast

milk.

177- 179

In the full- term well infant this does not produce

disease in the infant and is considered “natural immunization.”

ere is considerable debate concerning the risks of CMV

infection in premature or very- low- birth- weight infants. ere

are conicting data regarding the rates of symptomatic disease

in CMV acquired via breast milk in premature infants and

the occurrence of long- term sequelae in these infants.

178,180

e risk of transmission and long- term sequelae may be more

signicant for extremely premature infants less than 28 weeks’

gestational age. Because of the concern for signicant short-

term and possible long- term eects of postnatal infection with

CMV via breast milk, the Red Book Committee of the AAP has

issued some guidance. ey recommend considering screening

mothers of premature infants less than 32 weeks’ gestational

age and short- term pasteurization of breast milk prior to

administration to the infant.

181

Use of CMV- negative donor

human milk is another alternative. Across nurseries worldwide

there is no consensus practice because pasteurization also

inactivates many beneciary components of fresh breast milk.

ere is ongoing research on ash heating, freezing, and

irradiation for inactivation of CMV in breast milk without

inactivation of various biologically active components. Until

there is a broadly accepted consensus opinion, the conservative

approach would be to follow the AAP recommendation from

the Red Book Committee.

In mothers with hepatitis, identication of the etiologic

agent is required before the appropriate management can be

determined. Before the etiologic agent is identied, care must

include precautions for all potential organisms. Consultation

with an infectious disease specialist is oen appropriate.

For hepatitis A virus, infection in the newborn or young

infant is uncommon and not associated with severe illness.

Breastfeeding can continue, and if the diagnosis is made within

2 to 3 weeks of the infant’s initial exposure to the infected

mother, immune serum globulin and hepatitis A virus vaccine

given simultaneously can decrease infection in the infant. With

hepatitis B virus, the risk of chronic infection and its serious

complications are high (up to 90%) when infection occurs

perinatally or in early infancy. Hepatitis B immune globulin

and hepatitis B virus vaccine given simultaneously prevent

hepatitis B virus transmission in over 95% of cases, regardless of

whether the infant is fed by breast or bottle. erefore it is very

appropriate to continue breastfeeding along with provision of

eective immune therapy.

181

With hepatitis C virus (HCV) the rate of mother- to- child

transmission (MTCT) is about 6%. Several cohort studies

suggest that most infants acquire HCV infection in utero or in

the peripartum period. HCV has been detected in colostrum

and breast milk at low levels. Large cohort studies, including

1854 mother- infant pairs, have not shown a signicant

dierence in acquisition of HCV infection between breastfed

and formula- fed infants.

182

Guidelines from the CDC and AAP

state that maternal HCV infection is not a contraindication

to breastfeeding.

183

HCV and human immunodeciency

virus (HIV) coinfection in the mother is a contraindication

to breastfeeding in high- income countries. Because HCV

is a blood- borne virus, the CDC recommends avoiding

breastfeeding from the aected breast, at least temporarily, if an

HCV- infected mother experiences nipples that are cracked or

bleeding.

183

No clear data indicate HCV transmission via breast milk

in HIV- negative mothers.

184

ere is evidence of inactivation

of HCV by breast milk.

185

However, given the multiple issues

involved—low risk of HCV transmission via breast milk,

increased risk of transmission in association with HIV infection

or high levels of HCV RNA in maternal serum, lack of eective

preventive treatments (vaccines or immune serum globulin), and

the risk of chronic HCV infection and serious liver disease—it

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PART 1 Scientiﬁc Basis of Perinatal Biology

178

is essential to educate the parents about the possible low risks of

continued breastfeeding and the many benets of breastfeeding

in order to facilitate autonomous informed decision making.

Maternal retroviral infection and breastfeeding is a highly

controversial issue that continues to be evaluated and debated.

HIV type 1 (HIV- 1) is transmissible via breastfeeding and can

signicantly increase the risk of HIV infection in infants born

to HIV- positive mothers. One meta- analysis of ve studies

of infants born to HIV- infected mothers reported the risk of

HIV transmission to infants strictly from breastfeeding as

14% (95% condence interval [CI], 7% to 22%).

186

Among

the many concerns about HIV and breastfeeding are the risk

of transmission related to the duration of breastfeeding, the

relative risks of exclusive versus nonexclusive breastfeeding, the

risk of mortality and morbidity resulting from other infections

and malnutrition associated with not breastfeeding, the

signicance of HIV viral loads and CD4

T- cell counts in the

mother relative to transmission from breast milk, the potential

protective eects of breast milk against HIV infection, and the

degree to which antiretroviral therapy for the mother or infant

will be protective against HIV infection. Social issues involved

in this debate include the right of the mother to make choices

for herself and her infant, the social stigma of not breastfeeding

in certain cultures and communities, and the possibility that

breastfeeding rates in HIV- negative mothers will be adversely

aected by the advice given to HIV- positive mothers. In many

countries, neither choice is optimal: breastfeeding risks HIV

infection in the infant, but not breastfeeding increases the risks

of other infections and malnutrition. e lack of adequate data

from controlled trials about the various factors contributing

to infection adds to the diculty of making straightforward

recommendations applicable to diverse situations around

the world. In the United States, it is appropriate to advise no

breastfeeding for infants of HIV- infected mothers to decrease

the risk of HIV transmission to the infant.

187

In resource- poor settings, more recent review of the

available data on providing antiretroviral prophylaxis to either

the mother or the infant during pregnancy and lactation has

led to new recommendations from the WHO.

188,189

ese

include specic recommendations for the use of antiretroviral

therapy in women who need treatment for their own health, the

continuation of which beyond the postpartum period provides

additional protection against MTCT at the same time as allowing

the other benets to the infant from breastfeeding. e criteria

for initiating antiretroviral therapy for pregnant women are the

same as those for nonpregnant women. All HIV- infected women

who are not in need of antiretroviral therapy for their own health

should receive an eective antiretroviral prophylaxis regimen to

prevent MTCT. Eective antiretroviral therapy for the mother

can be continued through the period of lactation to protect the

infant. Additionally, the infant can receive antiretroviral therapy

to prevent against HIV infection via breastfeeding. HIV- infected

women should still receive education concerning the choices of

infant feeding, with emphasis on the benets of breastfeeding

in combination with antiretroviral prophylaxis provided to the

mother or infant for the duration of breast milk consumption.

Education, support, and medical care throughout lactation for

both mother and infant should be provided to achieve the goals

of 100% prevention of MTCT, optimal maternal health and

survival, and long- term infant health and survival.

ere are limited reports that deal with the risk of HIV

type 2 (HIV- 2) transmission via breastfeeding. Studies suggest

that HIV- 2 transmission via breast milk is less common than

HIV- 1 transmission.

190

However, until adequate information

is available, it is appropriate to use the same guidelines as for

HIV- 1.

Transmission of human T- cell leukemia virus type I

(HTLV- I) infection is associated with breastfeeding, although

short- term breastfeeding (less than 6 months) may pose no

greater risk than the risk for formula- fed infants.

191- 193

Japan, where high rates of infection with this virus occur,

proscription of breastfeeding is common. In the United

States, when the mother has documented HTLV- I infection,

it is appropriate to discuss the options, risks, and benets of

breastfeeding and to consider short- term breastfeeding. ere

are many uncertainties concerning HTLV type II, related to the

diseases associated with infection and to whether transmission

occurs via breast milk. Here again, it is appropriate to discuss

the available data with the parents and to include an infectious

disease consultant in the discussion to facilitate an autonomous

informed decision.

Complications of the Breast

ere are a variety of conditions that can manifest as palpable

breast masses during lactation. Some are lactation- specic and

some non- lactation- specic (see Table 11.4). Some of these

lactation- specic masses are more likely to require imaging

for diagnosis and management, such as galactocele, phlegmon,

abscess, lactating adenoma, and lactiferous sinus, among other

less common masses.

74,194,195

ACCESSORY BREAST TISSUE

Accessory tissue occurs in approximately 2% to 6% of women.

It oen rst manifests during the breast enlargement during

pregnancy. e tissue is frequently in the axilla and bilateral in

approximately one- third of women. Its presence can be acutely

obvious during engorgement of the breast.

PLUGGED DUCTS

Tender lumps in the breast in a mother who is otherwise well

are probably caused by plugging of a collecting duct. e best

treatment is to continue nursing while manually massaging

the area to initiate and ensure complete drainage. Holding

the infant in a dierent position may encourage ow, as may

application of hot packs before a feeding. If repeated plugging

occurs, a check should be made for possible obstruction from

a brassiere strap or other external forces. Some women can

actually see small plugs ejected when they massage. For some,

reducing polyunsaturated fats in the diet and adding lecithin

provides relief.

GALACTOCELE

Milk- retention cysts are uncommon and are usually associated

with lactation. e swelling is smooth, rounded, and

nontender. e cyst may be aspirated to conrm the diagnosis

and to avoid surgery, but it will ll up again. e cyst can be

removed with local anesthesia without interruption of the

breastfeeding routine. e diagnosis can also be conrmed by

ultrasound, by which the cyst and milk look similar but tumor

is distinguishable.

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11 The Breast and the Physiology of Lactation 179

MASTITIS

Mastitis is an infectious process in the breast producing

localized tenderness, redness, and heat, together with systemic

symptoms of a ulike illness with fever and malaise. It can be

distinguished from engorgement and plugged duct (Table 11.5).

Usually a red, tender, hot, swollen, wedge- shaped area of the

breast is visible, and it corresponds to a lobe (Fig. 11.9). e

common organisms are Staphylococcus aureus, Escherichia coli,

and, rarely, Streptococcus. An approach to managing mastitis

in the breastfeeding mother is outlined by the Academy of

Breastfeeding Medicine Protocol Committee; the major points

of management are as follows:

•

Breastfeeding should continue on both breasts, optimizing

eective milk removal.

•

Analgesia is appropriate and necessary to facilitate let-

down and eective milk removal.

•

Supportive measures, including rest, uids, adequate

nutrition, heat for let- down and cold for pain aer milk

expression, and home care support for the infant and the

mother are the rst line of management.

•

If the mastitis is not improving with conservative support-

ive measures, antibiotics appropriate to the probable cause

and relevant sensitivities should be prescribed.

•

Antibiotics are recommended by most practitioners for

10 to 14 days, but there are no controlled trials for the

eective duration of antibiotics. e antibiotic should be

safe for the infant (see Mastitis under Maternal Infec-

tions).

e most common cause of recurrent mastitis is delayed or

inadequate treatment of the initial disease. Mastitis can evolve

into formation of a phlegmon and/or an abscess, sometimes

necessitating drainage and/or imaging. In most situations of

mastitis, laboratory or diagnostic procedures are unnecessary.

Recommended exceptions to this include no response to

antibiotic therapy within 2 days, recurrence of mastitis,

hospital- acquired mastitis, medication allergies to the standard

antibiotics for mastitis, and severe cases of mastitis.

176

recurrence, cultures of a midstream ow of milk should be sent

and antibiotics chosen according to the results.

LACTATING ADENOMAS

ese are benign painless masses most frequently observed in

the upper outer quadrant of the breast. ey seem to present

spontaneously, are presumed to be due to hormonal secretion,

and oen resolve aer lactation ends. Biopsy is sometimes

Breast Masses

Lactation- Specific Clinical Findings Non- lactation- Specific Clinical Findings

Accessory breast tissue Common in axilla, bilateral in one-

third of cases, noticed most often

during pregnancy enlargement

Fibroadenoma Mobile rubbery smooth mass, asymptomatic

or tender

Plugged ducts Occur in areas of milk stasis Phyllodes tumor Fibroepithelial lesion similar to ﬁbroadenoma

Galactocele Common, “milk retention cyst,”

ﬂuid ﬁlled

Cysts With ﬁbrocystic disease or simple or complex

Phlegmon Poorly deﬁned collection of ﬂuid Intramammary lymph

nodes

Uncommonly palpated but usually identiﬁed

by the patient

Abscess Usually well- deﬁned, inﬂamed ﬂuid

collection

Fat necrosis Irregular palpable mass, tender or not

Lactating adenoma Rubbery or ﬁrm mass, fairly well-

circumscribed

Hematoma Tender mass, usually + history of obvious

trauma

Lactiferous sinuses Subareolar mass Periductal mastitis Squamous metaplasia of lactiferous ducts,

most commonly in smokers

Idiopathic

granulomatous

mastitis

Evolving inﬂammatory swellings

Breast cancer Variable presentations

Data from Mitchell KB, Johnson HM. Breast conditions in the breastfeeding mother. In: Lawrence RA, Lawrence RM, eds. Breastfeeding: A Guide

for the Medical Profession. 9th ed. St. Louis, MO: Elsevier; 2021 [chapter 16]; and Mitchell KB, Johnson HM, Eglash A, Academy of Breastfeeding

Medicine Clinical Protocol #30: Breast Masses, Breast Complaints, and Diagnostic Breast Imaging in the Lactating Woman. Breastfeed

Med. 2019;14(4):208–214. https://doi.org/10.1089/bfm.2019.29124.kjm.

TABLE

11.4

Comparison of Engorgement, Plugged Duct, and Mastitis

Onset Site

Symptom

Swelling and Heat Pain Body Temperature

Systemic

Symptoms

Engorgement Gradual,

immediately

after birth

Bilateral Generalized Generalized <38.4°C (101°F) Feels well

Plugged duct Gradual, after

feedings

Unilateral May shift; little or no

heat

Mild but

localized

<38.4°C Feels well

Mastitis Sudden, after

10 days

Usually unilateral Localized, red, hot,

swollen

Intense but

localized

>38.4°C Flulike

symptoms

From Lawrence RA, Lawrence RM. Breastfeeding: A Guide for the Medical Profession. 8th ed. St Louis, MO: Mosby; 2015:568.

TABLE

11.5

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PART 1 Scientiﬁc Basis of Perinatal Biology

180

recommended to conrm the diagnosis but breastfeeding can

continue.

LACTIFEROUS SINUSES

ese are relatively “dilated” lactiferous sinuses palpable beneath

the areola. ey are more noticeable in breastfeeding women

than in those who have stopped breastfeeding.

CANDIDIASIS OF NIPPLE AND BREAST

Candidiasis of the breast is frequently overdiagnosed because

there are several causes for the breast pain that is described by

mothers as feeling like “a stab with a hot poker.” On examination,

there may be little to see except a pinkish hue or slight darkening

to the nipple and central areola. Rarely are white plaques seen

on the nipple. If the mother has a history of vaginal candidiasis,

the infant’s mouth may have become colonized, and this could

have resulted in inoculation of the nipples. e infant should

also be examined for both thrush and diaper rash and treated

simultaneously with the mother for a full 2 weeks. Nystatin

ointment is applied aer each feeding to nipples and areolae,

and the infant receives nystatin drops orally to the oral mucous

membranes aer each feeding. For a recurrent episode, the

mother can be treated with 200 mg oral uconazole systemically

once daily for 7 to 14 days. e infant can be given 6 mg/kg

on day 1 and then 3 mg/kg per dose every 24 hours orally.

Paciers and bottle nipples that are put in the mouth should

be discarded and new ones sterilized daily. Persistent thrush

requires a complete evaluation of the mother and may require

treatment for vaginal thrush, decreased sugar in the diet, and

colonization with lactobacillus by capsule or yogurt. Persistent

pain (longer than 2 weeks) with breastfeeding is an important

situation necessitating evaluation and management. Berens and

colleagues provide an approach to management and detailed

discussion of potential causes of persistent pain.

127

Medications While Breastfeeding

Questions about medication during breastfeeding are very

common. e transfer of maternal drugs to the infant during

lactation is dierent from transfer to the fetus during pregnancy.

Although it is almost always better to breastfeed, the mother

must weigh the potential benets and risks of a medication for

herself and her infant against the substantial benet of being

breastfed for the infant. e risk- benet ratio diers for each

drug and clinical setting. Both scientic information and

experienced clinical judgment are required to assess the risks

and benets and to determine the therapeutic choice.

e AAP Committee on Drugs has published a list of

commonly used drugs and chemicals that may transfer into

human milk.

196

e categories from the AAP list

196

are as

follows:

1. Cytotoxic drugs that may interfere with cellular metabo-

lism of the nursing infant

2. Drugs of abuse for which adverse eects on the infant

during breastfeeding have been reported

3. Radioactive compounds that require temporary cessation

of breastfeeding

4. Drugs for which the eect on nursing infants is unknown

but that may be of concern—for example, bromocriptine,

ergotamine compounds, and lithium

5. Drugs that have been associated with signicant eects

on some nursing infants and should be given to nursing

mothers with caution

6. Maternal medication usually compatible with breastfeed-

ing

7. Food and environmental agents that might have an eect

on the breastfeeding infant

ere are various printed and online resources which

can be consulted concerning the use of medications in

lactation.

69,84,85,197

A readily available and frequently updated

handbook by omas Hale, Medications and Mothers’ Milk,

provides a scale that is roughly the reverse of the long-

established classication system developed by the AAP.

198

e

basic denitions from Hale’s text are as follows:

•

L1: safest

•

L2: safer

•

L3: moderately safe

•

L4: possibly hazardous

•

L5: contraindicated

A lack of information about a drug does not necessarily require

cessation of breastfeeding. Understanding the pharmacology

of a drug, the dosing schedule, and the stage of growth and

development of the infant inform the decision about whether it

would aect the infant. Characteristics of the drug that inuence

its passage into milk include the size of the molecule, its solubility

in lipid or water, whether it binds to protein, the pH, and the

diusion rates (Box 11.4). e route of administration inuences

the blood levels and therefore the milk levels. Passive diusion is

the principal transport mechanism. How the drug is metabolized

inuences whether it is present in the milk in its active form or as

an inactive metabolite (Fig. 11.10).

e infant’s ability to absorb, digest, metabolize, store, and

excrete a drug must be considered when choosing a medication

for a nursing mother. A drug that is not orally bioavailable will

not be absorbed from the milk by the infant. e ability to absorb

and metabolize a drug depends on the infant’s developmental

and chronologic age. An 18- month- old who nurses briey

about four times a day for comfort will get little medication, has

a substantial diet other than mother’s milk, and can metabolize

and excrete more eciently than a newborn. In the rst weeks

of life, the maturation or gestational age should be considered

when determining the safety of a medication, because the less

mature the infant is, the less mature are the liver and kidneys.

Figure 11.9 Mastitis of right breast, upper outer quadrant. (From

Lawrence RA, Lawrence RM. Breastfeeding: A Guide for the Medical

Profession. 7th ed. St. Louis, MO: Mosby; 2010:554.)

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11 The Breast and the Physiology of Lactation 181

With the exception of radioactive compounds such as

iodine 131, there is no drug whose possible presence in the

milk would require immediate withholding of breastfeeding

because the physician does not know the data. e American

College of Radiology has produced a manual for contrast

agents; based on reports from their analysis of the data, less

than 1% of the maternal dose is excreted in the breast milk, and

less than 1% of the contrast in breast milk reaching the infant’s

gastrointestinal tract is absorbed.

199

Box 11.5 provides some

salient points for the use of radiologic and nuclear medicine

studies during lactation. erefore arbitrary interference with

breastfeeding until information can be obtained is not justied.

Ample references and information lines are available to resolve

the issue. For medications used once or for a short time (e.g.,

anesthesia), the time required for the drug to clear the mother’s

system and her milk can be determined. e mother can pump

and discard her milk for that period if deemed necessary using

evidence- based resources and return to breastfeeding (usually

in a few hours or days, not weeks).

MILK- TO- PLASMA RATIO

e milk- to- plasma ratio, a term applied to drugs being used

by a lactating mother, indicates the level of the drug in the milk

compared with the level in the plasma at a given time. e

dosage of the drug, including time and route of dosing, must

be known to interpret the milk- to- plasma ratio. If there is a

very low level in the plasma and the same very low level in the

milk, the ratio is close to or equal to 1. A ratio of 1 suggests

that the level is of concern; however, the actual level in milk is

low and therefore the risk to the infant is likely to be low. Most

drugs have a milk- to- plasma ratio of less than 1. It is important

to know peak plasma and peak milk levels, and peak plasma

and peak milk times, to make appropriate recommendations

to avoid feeding the infant when transfer of the drug would be

greatest.

ANALGESIA AND ANESTHESIA FOR THE

BREASTFEEDING MOTHER

e appropriate use of analgesia and anesthesia during labor and

delivery and in the peripartum period, as well as at other times

for the breastfeeding mother, is a skill that every obstetrician

should master. e use of pharmacologic agents for pain relief

during labor and in the postpartum period is appropriate and

may improve outcomes for the infant and mother. eir use

may inuence the course of labor, the neurobehavioral status

of the infant, and the initiation of breastfeeding. e eects

of such analgesic or anesthetic medications on lactation will

depend of various factors, such as the age and size of the infant,

the ability of the infant to clear the quantity of medication he

or she is exposed to, and the stage of lactation. Pain, suering,

fear, and anxiety during labor can aect delivery and have a

negative eect on breastfeeding. ese issues may necessitate

pharmacologic treatment, but continuous support in labor and

nonpharmacologic management of pain may decrease the need

for medications and facilitate early skin- to- skin contact and

initiation of breastfeeding. Appropriately referenced guidelines

for analgesia and anesthesia use in lactating women are available

from the Academy of Breastfeeding Medicine.

200

Box 11.6

presents a few salient points from these guidelines.

Ongoing Breastfeeding Support

The duration of lactation will vary significantly by mother-

infant dyad. Support should be given to every mother and

family to maintain her milk supply, continue breastfeeding,

and meet her breastfeeding goals. This is especially

important when the mother and infant are separated for

longer periods of time, as might occur with maternal

hospitalization, surgery, or return to work or school, some of

the more common examples of separation. One of the more

effective practices that can assist mothers in maintaining

their milk supply involves creating a “breastfeeding- friendly

physician’s office.”

201

Overall, this involves providing an

office environment that is supportive of breastfeeding, which

1. Mammary alveolar epithelium represents a lipid barrier with

water- ﬁlled pores and is most permeable for drugs during

the colostral phase of milk secretion (ﬁrst postpartum week).

2. Drug excretion into milk depends on the drug’s degree of

ionization, molecular weight, solubility in fat and water, and

relationship of pH of plasma (7.4) to pH of milk (7.0).

3. Drugs enter mammary cells basally in the nonionized, non-

protein- bound form by diffusion or active transport.

4. Water- soluble drugs of molecular weight less than 200 pass

through water- ﬁlled membranous pores.

5. Drugs leave mammary alveolar cells by diffusion or active

transport.

6. Drugs may enter milk via spaces between mammary alveolar

cells.

7. Most ingested drugs appear in milk; drug amounts in milk

usually do not exceed 1% of ingested dosage, and levels in

the milk are independent of milk volume.

8. Drugs are bound much less to milk proteins than to plasma

proteins.

9. The drug- metabolizing capacity of mammary epithelium is

not understood.

Data from Lawrence RM, Lawrence RA. Medications, herbal prepara-

tions, and natural products in breast milk. In: Lawrence RA, Law-

rence RM. Breastfeeding: A Guide for the Medical Profession. 9th

ed. St. Louis, MO: Elsevier; 2021;332.

BOX 11.4 THE PASSAGE OF DRUGS INTO BREAST

MILK

Gut

Lungs

Skin

Storage

Excretion

Absorption Bloodstream

(bound and unbound)

Distribution to tissues

Membrane

















Live

atBrain Kidney Breast Bone

Metabolism

Interaction

Excretion

Storage

Figure 11.10 Distribution pathways for drugs. Distribution path-

ways vary with the drug and are relevant to advising the lactating mother

about breastfeeding when drugs have been prescribed. IM, Intramus-

cular; IV, intravenous. (Modiﬁed from Rivera- Calimlim L. Distribution

pathways for drugs, once absorbed during lactation. Clin Perinatol.

1976;14:51.)

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PART 1 Scientiﬁc Basis of Perinatal Biology

182

can include such specific practices as providing appropriate

written and audiovisual breastfeeding materials in the office,

providing a private lactation room, offering prenatal and

postnatal visits with an emphasis on breastfeeding, ensuring

access to a lactation consultant, and providing positive

feedback for breastfeeding from the staff and clinicians. Of

note, some of the same factors that contribute to successful

breastfeeding will facilitate the maintenance of the milk

supply during times of separation: early skin- to- skin contact

and suckling within the first hour of life, emphasis on early

feeding cues and correct technique, encouraging “instinctual

breastfeeding behaviors” for both the mother and infant,

202

and encouraging exclusive and unrestricted (on- demand)

breastfeeding. Mothers should be instructed on how to

express their milk, appropriately store it for home use, and

maintain lactation. Not every woman needs a pump. Every

woman should be trained how to manually express her breasts

before she leaves the hospital because this will facilitate her

managing common problems such as a plugged duct or

engorgement. Patient information on hand expression of

milk and a demonstration video are available online.

203,204

Hand pumps, battery- powered pumps, and electrical pumps

are available. The most effective expression of milk will

vary from woman to woman, but the expression should be

comfortable and meet the infant’s and mother’s needs.

As part of the normal discussion of ongoing lactation, the

mother should be asked about potential periods of separation

from her infant and in particular about her plans for return to

work or school as an introduction to the topics of human milk

storage for home use and the maintenance of lactation. Box

11.7 provides recommendations concerning human milk home

storage and use.

205

ONGOING BREASTFEEDING SUPPORT WITH

SOCIAL CHALLENGES

Substantial inequities exist in breastfeeding initiation and

duration by age, race/ethnicity, and socioeconomic status.

Reviewing CDC breastfeeding data by race/ethnicity, Black

non- Hispanic mothers had the lowest breastfeeding rates in

2017 across all parameters (Table 11.6).

206

Breastfeeding rates

assessing initiation, duration, and exclusivity were lower among

women who were less educated, were younger, were unmarried,

had lower household incomes, and received WIC. Obstetricians

1. Various organizations have made recommendations regard-

ing breast imaging in pregnant and lactating women (Ameri-

can College of Radiology [ACR], National Comprehensive

Cancer Network [NCCN], Journal of Radiographics, Academy

of Breastfeeding Medicine [ABM], among others).

2. Screening mammography should be done based on the

woman’s individual risk and expected duration of lactation.

Ultrasound can be used as a supplemental screening test with

mammography. Magenetic resonance imaging (MRI) can be

used in high- risk women breastfeeding for short periods of

time, 3 months after cessation of lactation.

3. Diagnostic breast imaging during lactation is the same as for

nonlactating women. Breast imaging by screening or diagnostic

mammography, ultrasound, or MRI with gadolinium- based intra-

venous contrast does not require interruption of breastfeeding.

4. “Pump and dump” after imaging studies is not appropriate.

No breastfeeding interruption is necessary for noncontrast

radiographs, nonvascular administration of iodinated con-

trast, computed tomography (CT) with iodinated intravenous

contrast, MRI with gadolinium- based intravenous contrast,

nuclear medicine imaging (positron emission tomography

[PET] scan or bone scan).

5. The calculated dose of an infant’s systemic exposure due to

a CT scan with iodinated intravenous contrast given to the

mother is <0.01% of the mother’s intravenous dose (less than

1 % of the dose administered to the mother reaches the breast

milk and <1% of the contrast ingested by the infant in the milk

is absorbed by the gastrointestinal tract). Similarly, the calcu-

lated dose of an infant’s systemic exposure when a mother un-

dergoes an MRI with gadolinium- based intravenous contrast

is <0.0004% of the mother’s dose (less than 0.04% of the ma-

ternal dose is excreted in breast milk and <1% of the ingested

contrast is absorbed form the infant’s gastrointestinal tract).

6. Thyroid imaging with I- 131 necessitates cessation of breast-

feeding for this child due to high gamma energy, high beta

emission, and long half- life (8.04 days). Thyroid imaging with

I- 123 is accompanied by recommendations for cessation

of breastfeeding varying up to 3 weeks (half- life 13 hours).

Technetium- 99m pertechnetate with its shorter half- life (6

hours) may necessitate interruption of breastfeeding for 4

hours up to 12 to 24 hours depending on the dose and the

recommendation of the local nuclear medicine specialist.

7. Renal imaging utilizing Tc- 99m DTPA, Tc- 99m MAG3, Tc- 99m

DMSA, or Tc- 99m glucoheptonate usually do not require ces-

sation of breastfeeding,

although the International Atomic

Energy Administration (IAEA) recommends withholding

breastfeeding for 4 hours for the possibility of any exter-

nal radiation and free Tc- 99m pertechnetate in the imaging

product.

8. Cardiac imaging with Tc- 99m Sestamibi or Tc- 99m Tetrofos-

min usually do not require cessation of breastfeeding.

Mul-

tigated acquisition scan (MUGA) with Tc- 99m labeled RBCs

can be used to assess left ventricular ejection fraction. No

interruption of breastfeeding is necessary for in vitro labeling,

but a 6- to 12- hour interruption is recommended for in vivo

labeling of the RBCs.

a,b

An echocardiogram is an alternative

method of assessing ventricular ejection fraction.

9. VQ scan is used to evaluate for pulmonary embolism. No

breastfeeding interruption is needed for the ventilation

agents of the scan, although a 12- hour interruption is recom-

mended for the perfusion agent Tc- 99m macroaggregated

albumin.

10. Mothers exposed to an accidental, unexpected radiation ex-

posure should be assessed by the institutional radiology safe-

ty ofﬁcer (RSO), and recommendations can be sought from

other expert sources (Infantrisk.com or MotherToBaby.org).

Expressed milk obtained during that period of interruption of breastfeeding can be stored, refrigerated, and given to the infant later after 10

physical half- lives or ∼60 hours, which will lead to the elimination of the radiation.

Although the International Atomic Energy Administration (IAEA) recommends withholding breastfeeding for 4 hours for the possibility of any

external radiation and free Tc- 99m pertechnetate in the imaging product.

Data from Mitchell KB, Fleming MM, Anderson PO, Giesbrandt JG, and Academy of Breastfeeding Medicine. ABM Clinical Protocol #31: Radiol-

ogy and Nuclear Medicine Studies in Lactating Women. Breastfeed Med. 2019;14(5):290–294. https://doi.org/10.1089/bfm.2019.29128.kbm.

Epub 2019 May 20. Accessed January 9, 2021; and American College of Radiology Committee on Drugs and Contrast Media. American College

of Radiology Manual on Contrast Media. 2020. https://www.acr.org/- /media/ACR/ﬁles/clinical- resources/contrast_media.pdf Updated 2020.

Accessed January 31, 2021.

BOX 11.5 USE OF RADIOLOGY AND NUCLEAR MEDICINE STUDIES DURING LACTATION

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11 The Breast and the Physiology of Lactation 183

1. Mothers who have received general anesthesia with healthy

term or older infants can generally resume breastfeeding as

soon as they are awake, stable, and alert.

2. Infants at risk for apnea, hypotension, or hypotonia may ben-

eﬁt from a brief interruption of breastfeeding (6–12 hours) af-

ter maternal anesthesia. In this situation, mothers can express

and store milk in small amounts to be used when the infant is

older, or it can be mixed with fresh milk containing no medica-

tions to dilute the medications present.

3. The most concerning class of medications used for anesthesia

and analgesia in breastfeeding mothers is opioids, as these

medications transfer into breast milk and may cause infant se-

dation or apnea. Judicious use of opioids for short periods is

likely to be safe for most breastfeeding mothers and infants.

4. Drugs used for induction, such as propofol, midazolam,

etomidate, or thiopental, enter the milk compartment only

minimally due to their extraordinarily brief plasma distribu-

tion, and hence their transport to milk is low to nil.

5. Little has been reported on the use of anesthetic gases in

breastfeeding mothers, but they also have brief plasma distri-

bution phases and milk levels are likely to be nil.

6. Neuromuscular blocking agents are safe for the breastfeeding

infant, as they have low lipid solubility and are largely distribut-

ed in the extracellular ﬂuid volume. There is little or no data on

the pharmacokinetics of these drugs in breast milk, but based

on their physical characteristics and their poor oral availability,

they are considered safe for use in the breastfeeding mother.

7. For women undergoing postpartum tubal ligation, interrupt-

ing breastfeeding is not indicated because the volume of co-

lostrum an infant would receive is small.

8. Women who receive single doses of medication for sedation

and analgesia for short procedures can breastfeed as soon as

they are awake and stable.

9. Local anesthetics such as lidocaine, bupivacaine, and ropi-

vacaine can be safely used in breastfeeding mothers. These

and other local anesthetics are poorly absorbed orally and the

large, polarized molecules do not easily transfer into milk.

10. Regional anesthesia (spinal, epidural, or peripheral nerve

block) should be considered whenever possible for intraop-

erative anesthesia or postoperative analgesia. It reduces the

need for intraoperative medications and may also decrease

the amount of pain medication needed postoperatively. This

may leave the mother more awake and alert in the immediate

postoperative period, and she will therefore be more likely to

resume breastfeeding sooner.

11. Antiemetics are used commonly in the perioperative period,

and most of these medications are considered safe during

breastfeeding. Ondansetron, dexamethasone, and metoclo-

pramide may be preferred because of their lack of sedating

side effects. Prochlorperazine, promethazine, and scopol-

amine are likely safe, but may lead to maternal sedation. Pro-

methazine and scopolamine have been noted to affect milk

supply if given repeatedly.

Modiﬁed from Reece- Stremtan S, Campos M, Kokajko L, and the Academy of Breastfeeding Medicine. ABM Clinical Protocol #15: Analgesia and

Anesthesia for the Breastfeeding Mother, Revised 2017. Breastfeeding Medicine. 2017;12(9):1–7. https://doi.org/10.1089/bfm.2017.29054.srt.

BOX 11.6 ANESTHESIA FOR SURGERY IN BREASTFEEDING MOTHERS

PREPARATION FOR HUMAN MILK STORAGE

1. Women should wash their hands before expressing breast milk

(using soap and water or a waterless hand cleanser).

2. Milk expression can be done by hand or by a pump. A va-

riety of pumps are available, and selection can be based on

cost, availability, frequency and duration of expression, time

constraints, and comfort, etc. Appropriate cleaning of hands

and cleaning of pump parts (per manufacturer’s instructions)

is adequate to limit milk contamination during expression and

storage. The CDC has guidelines for pump cleaning available

on their website.

3. Only food- grade plastic containers should be used for human

milk storage. There are a variety of studies concerning storage

containers and their effects on fat, carbohydrate, protein IgA,

and white blood cell content of the milk after storage. Glass

and polypropylene containers are frequently used. The plastic

bags used for human milk storage should be sturdy, easily and

effectively sealed, and readily labeled (name of child and date

of milk expression). The bags should be stored in an area of

the freezer to minimize damage to the bag. Containers made

with bisphenol A or S should be avoided due to the potential

effect the containers have on the milk during storage. Human

milk should not be stored in hospital plastic specimen storage

containers used for other bodily ﬂuids.

4. Containers for human milk storage do not have to be sterilized.

Washing in hot soapy water with careful rinsing and thoroughly

drying (by air or paper towels) is sufﬁcient. If soap is not readily

available or water is limited, boiling them in water and cool-

ing prior to use may be the preferred method of preparation.

Chemical disinfection is not recommended.

5. There is no need to discard the ﬁrst few drops of milk at the

beginning of milk expression.

6. The mother’s breasts and nipples do not need to be washed

prior to milk expression.

MILK STORAGE GUIDELINES

Location of

Storage Temperature

Maximum

Recommended Storage

Duration

Room

temperature

16–29°C

(60–85°F)

4 hours optimal

6–8 hours acceptable

under very clean

conditions

Refrigerator ∼4°C (39.2°F) 4 days optimal

5–8 days under very

clean conditions

Freezer <−4°C (24.8°F) 6 months optimal

12 months acceptable

USING STORED HUMAN MILK

1. Fresh milk is better than frozen milk; use the oldest milk ﬁrst

from the refrigerator or freezer.

2. Avoid using containers that have leaked or been rewarmed

and recooled or refrozen.

3. Stored milk may have altered smell and taste due to enzymatic

breakdown. This breakdown of fats can aid in digestion and is not

harmful; however, some infants may refuse to drink it. Milk that

appears stringy, foul, or purulent should not be fed to the infant.

4. The infant may drink the milk cool, at room temperature, or

warmed, and infants may demonstrate a preference.

5. Defrost the stored milk in the refrigerator overnight, in run-

ning warm water, or by setting it in a container of warm water.

Do not microwave the milk.

6. Previously frozen human milk, thawed in the refrigerator for 24

hours, should be used within a few hours at room temperature.

7. Avoid refreezing thawed human milk, due to lack of safety

information on its reuse.

BOX 11.7 INFORMATION ON STORAGE OF HUMAN MILK FOR HOME USE WITH FULL- TERM INFANTS

Continued

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PART 1 Scientiﬁc Basis of Perinatal Biology

184

need to understand and address structural determinants of

health such as transportation, access to lactation/postpartum

support, and paid family leave in order to eliminate breastfeeding

inequities. For example, in 2012, 23% of women living in the

US returned to work as early as 10 days postpartum,

207

making

mental wellness, maternal- infant bonding, and establishment of

breastfeeding extremely challenging in that short time frame. To

address the health care inequities associated with breastfeeding,

the obstetrician should understand the varied causes of health

disparities and recognize that the solutions must occur at

the patient level, practitioner level, health care system level,

institution level, and at the level of policy and programs.

208,209

Antiracism health care is paramount to demolish the negative

impact of racism, not race, on health care outcomes.

e social challenges in health care and the threats to

equitable, nondiscriminatory health care facing mothers and

families extend into the lesbian, gay, bisexual, transgender,

queer/questioning, plus (+) (LGBTQ+) community.

79,210

Individuals from this community have experienced stigma,

misunderstanding, and inadequate care due to prejudice and

lack of understanding of individual needs. Here also there are

tremendous opportunities to provide arming, respectful

health care. ese can begin with the respectful use of language

and terms, education of health care providers, providing

gender- neutral bathrooms, displaying inclusive signage in

the health care facility, and understanding the signicance of

gender- arming medical and surgical treatments on pregnancy

and breastfeeding/chestfeeding. (For example, chestfeeding

8. It is reasonable to discard milk leftover from a feeding within

1–2 hours (based on limited information). Storing milk in small

volume increments (15, 20, or 60 mL) may limit wasting or

discarding unfed amounts of milk.

9. Expressed human milk does not require special handling (e.g.,

universal precautions) as is recommended for other bodily ﬂu-

ids (such as blood, urine). It can be stored in any refrigerator

with other stored foods, labeled and dated, although moth-

ers may prefer to store their milk in a personal container.

10. Uncontaminated human milk naturally contains nonpatho-

genic bacteria, which is important to establishing normal neo-

natal intestinal ﬂora. There is no evidence that stored milk

from a mother with breast pain due to infection needs to be

discarded.

Centers for Disease Control and Prevention. How to Keep Your Breast Pump Kit Clean: The Essentials. https://www.cdc.gov/healthywater/

hygiene/healthychildcare/infantfeeding/breastpump.html Reviewed July 8, 2020. Accessed January 9, 2021.

Data from Eglash A, Simon L, and the Academy of Breastfeeding Medicine Protocol Committee. ABM Clinical Protocol #8: Human Milk Storage

Information for Home Use for Full- Term Infants. Revised 2017. Breastfeeding Med. 2017;12(7):390–395. https://doi.org/10.1089/bfm.2017.29047.

aje.

BOX 11.7 INFORMATION ON STORAGE OF HUMAN MILK FOR HOME USE WITH FULL- TERM INFANTS—cont’d

Rates of Any and Exclusive Breastfeeding by Sociodemographic Status Among Children Born in 2017

ANY BREASTFEEDING (BF) (%) EXCLUSIVE BREASTFEEDING (EBF) (%)

Ever BF BF at 6 months BF at 12 months

EBF through 3

months

EBF through 6

months

RACE/ETHNICITY

Hispanic 84.1 55.4 33.9 41.5 21.5

Non- Hispanic White 86.7 61.9 38.2 52.4 28.7

Non- Hispanic Black 73.7 47.8 26.1 38.7 21.2

Non- Hispanic Asian 90.0 73.5 50.0 47.7 26.8

Non- Hispanic Hawaiian/Paciﬁc Islander 85.2 NA NA NA NA

Non- Hispanic American Indian/Alaska Native 80.7 NA NA NA NA

2 or more races 83.7 56.5 31.0 43.9 26.6

MATERNAL EDUCATION

Less than high school 73.6 49.0 28.9 30.8 17.1

High school graduate 75.6 44.1 25.7 41.7 21.5

Some college/ technical school 84.7 53.6 31.1 45.4 23.3

College graduate 93.3 74.0 46.6 57.2 32.8

AGE

Younger than age 20 74.0 NA NA NA 18.7

20–29 82.4 50.9 28.6 45.4 24.2

30 or older 85.2 62.7 39.2 47.8 26.5

MARITAL STATUS

Married 89.7 68.2 43.7 53.7 30.6

Unmarried 75.1 42.5 21.8 36.1 17.6

RECEIVING WIC

Yes 77.0 45.4 24.8 37.3 19.0

No, but eligible 82.1 61.3 43.4 53.8 31.1

Ineligible 92.1 71.4 44.8 55.7 31.3

From Centers for Disease Control and Prevention. Rates of Any and Exclusive Breastfeeding by Socio- demographics among Children Born in 2017

[updated 08/01/2019]. https://www.cdc.gov/breastfeeding/data/nis_data/rates- any- exclusive- bf- socio- dem- 2017.htm.

TABLE

11.6

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11 The Breast and the Physiology of Lactation 185

describes the action of a masculine- identied trans person in

feeding their baby at the chest with or without previous surgery

to aect existing mammary tissue.) Options regarding fertility

(childbearing) and contraception should be explored with

both parents, as should expressing or pumping breast milk,

inducing lactation, sharing of infant feeding, colactation of an

infant by two or more parents, bonding of the infant with each

parent, use of donor milk and informal milk sharing, and the

plans for parenting and support for the parents/family at home

with or without breastfeeding. Some of these opportunities for

creating and expanding respectful health care during pregnancy

and lactation are reviewed by the Academy of Breastfeeding

Medicine in their clinical protocol on lactation care for

LGBTQ+ patients.

ere remains a tremendous amount of

work for each of us and all of us to do in collaboration with

our patients to combat prejudices and institutional racism

and create equitable, respectful lactation care for all mothers,

partners, and all families.

Key Points

•

Mother’s milk is the most appropriate feeding for the

infant in the rst 6 months of life. It is ideal to continue

mother’s milk, while adding weaning foods, for the next 6

months and as long as mother and baby wish.

•

ere are very few true contraindications to the use of the

mother’s own milk for her infant. Maternal use of drugs

of abuse should be limited if possible and breastfeeding

continued considering the individual medications and

the actual maternal doses. Specic maternal infections

can be a contraindication to breastfeeding: HIV; HTLV-

I; Ebola, Marburg, Lassa, and dengue viruses; and active

pulmonary tuberculosis. Most maternal infections can be

treated without interrupting breastfeeding. If the infant

has the severe form of galactosemia, that can be a contra-

indication to breastfeeding.

•

e obstetrician plays an important role in support of

breastfeeding, beginning with the rst prenatal visit,

through pregnancy, at delivery, during the hospital stay,

and as long as the mother requires assistance.

•

A good understanding of the anatomy and physiology of

the breast and the physiology of lactation is essential to

guiding and assisting lactating mothers to achieve their

breastfeeding goals.

•

Establishing a breastfeeding- friendly oce and hospital

environment is essential to breastfeeding success.

•

Obstetricians, pediatricians, and lactation professionals

should work together to establish a knowledgeable and

skilled environment for successful breastfeeding. ere are

numerous current resources of information, readily avail-

able to practitioners, to optimize the care of breastfeeding

mothers and infants.

SUGGESTED READINGS

Briggs GG, Freeman RK, Towers CV, Forinash AB. Drugs in Pregnancy and Lac-

tation. 11th ed. Philadelphia: Lippincott Williams & Wilkins; 2017.

Hale TW. Medications and Mothers’ Milk. 17th ed. Amarillo, TX: Hale; 2017.

Lawrence RA, Lawrence RM. Breastfeeding: A Guide for the Medical Profession.

9th ed. St. Louis: Mosby; 2021.

Family Larsson- Rosenquist Foundation. In: Breastfeeding and Breast Milk: From

Biochemistry to Impact. Stuttgart, Germany: ieme; 2018.

A full reference list is available online at ExpertConsult.com.

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185.e1

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