Breast-feeding in the United States has continued to experience a pronounced resurgence since the early 1970s. Slightly more than 60% of all women who are hospitalized for birth breast-feed their infants. The duration of lactation also has increased,¹ although it is still uncommon for women in the United States to continue breast-feeding through the infant's first year, as recommended by the American Academy of Pediatrics.²

Mothers who breast-feed their infants have been characterized as being middle class, married, and white, and as having some college education and one or two children. Women in other situations also are breast-feeding their infants, so to assume that an unmarried nonwhite teenager is unlikely to breast-feed her child is unwise. Some of the greatest increases in breast-feeding initiation rates occur among nonwhites.¹ In one study, there was no difference in breast-feeding duration rates when low-income, often nonwhite, single women were provided information and support for breast-feeding during the prenatal and early postpartum periods.³

Factors that influence the decision to breast-feed and its duration are prenatal support and information,⁴ support in the early postpartum period,⁵ attitudes and management suggestions by health professionals,^6,7 timing of any obstetric advice,⁸ any previous infant feeding experience,⁹ mode of delivery,¹⁰ mother-infant separation in the early neonatal period,¹¹ and patterns of maternal employment soon after the infant's birth.¹²

Most well-nourished mothers successfully breast-feed their infants without need for significant dietary changes. Nutritional requirements during lactation and specific nutritional concerns are addressed in this chapter. How the special maternal and infant needs can be met while encouraging lactation also is discussed.

Fluid

When a breast-fed infant has poor weight gain or is acting fussy and dissatisfied, the mother is often told to drink more fluids. Dusdieker and co-workers¹³ found that women consuming an average of 2000 ml of fluid each day produced an average of 814 ml of milk in 24 hours. Increasing fluid intake by 25% had no effect on milk production.

Several studies in underdeveloped countries showed a decrease in milk volume in severely malnourished mothers.¹⁴ In these studies, the mothers' milk volume was increased from an average of 742 ml to 872 ml per day by supplemental food programs providing increased calories and protein.¹⁴

Energy

Estimates of the energy required for milk production vary from 60% to 90% efficiency in converting maternal kilocalories ingested into the kilocalorie content of breast milk. Using the figure of 90% suggested by Worthington and colleagues,¹⁵ 945 kcal is required to produce 850 ml of human milk. An average of 5.2 kg of weight gained during pregnancy is not accounted for by the fetus or other components, and it is assumed that some of this weight gain is used to meet the energy requirements for breast-feeding.¹⁶ The United States recommended daily allowance for calories for breast-feeding is 2700 kcal/day for mothers 15 to 23 years old and 2400 kcal/day for mothers 23 years or older (Table 1).¹⁷

TABLE 1. Recommended Daily Allowances for Selected Nutrients for Nonpregnant, Pregnant, and Lactating Women*

An evaluation of successful and unsuccessful lactation, as defined by the need to offer supplemental bottle feedings during the infant's first 2 months of life, found that all of the mothers who were successfully breast-feeding their infants were eating more than their previous normal volume of food.¹⁸ Mothers who were unsuccessful in breast-feeding were consuming fewer than 2000 kcal/day, and many of them reported that they felt a need to diet. Whichelow¹⁹ concluded that mothers must be informed of their extra caloric requirements during lactation and that they should be advised to eat more if they are concerned about the adequacy of their milk supply.

Butte and associates²⁰ also found that successful lactation was compatible with gradual weight reduction in the mother whose energy intake was less than the current recommendations. They concluded that maternal ingestion of approximately 2200 kcal/day was adequate for both appropriate milk production and gradual reduction in maternal weight loss.²⁰

Protein

The average protein content of human milk from healthy mothers is 1.09 g/dl compared with 0.93 g/dl from chronically malnourished mothers. Approximately 25% of the nitrogen in milk is from nonprotein sources.²¹ Women who are chronically malnourished generally weigh 10% or more less than their ideal body weight, are from underdeveloped countries, or follow strict vegetarian diets, consuming less than 50 g of protein/day.

A healthy mother consuming 65 to 75 g of protein/day needs no additional dietary protein. In some studies in underdeveloped countries, protein supplementation resulted in increased protein content of human milk and increased daily weight gain of the infant.²¹

Carbohydrates

Approximately 90% of the carbohydrate in human milk is lactose. The amount of lactose in human milk is relatively constant at 7.3 to 7.4 g/dl, and appears to be independent of the maternal carbohydrate ingestion.²² Because of its constant concentration, lactose is thought to be the regulating factor in the volume of human milk produced.

Fat

Fat is the major source of calories in human milk. The average fat content is between 3% and 3.5%.²³ Changes in maternal diet affect the fatty acid composition but not the total fat content of breast milk.²³ Short-chain fatty acids (up to 16 carbons) may be synthesized in the mammary glands. Maternal plasma triglycerides are the source of long-chain fatty acids and cholesterol in breast milk.²⁴

The recent change in the American diet toward increased intake of vegetable fats rather than animal fats is reflected in a human milk fatty acid content, with increased long-chain fatty acids and an increase in linoleic acid.²⁴ Human milk produced by vegetarian mothers also shows high levels of linoleic acid.²⁵ Manipulation of the maternal diet does not appear to alter the cholesterol content of human milk significantly.²⁶

When the mother is taking inadequate calories so that she is using her own fat stores for milk production, her milk still contains 3% to 3.5% fat, but the fatty acid composition resembles the composition of her fat stores.^27,28 Similarly, total milk fat content is the same when maternal caloric sources are chiefly protein and carbohydrate. However, milk composition changes and levels of saturated fatty acids increase as lipids are synthesized from fat stores and are not merely carried as plasma triglycerides from the portal system to the mammary gland.^26,27 A restricted maternal diet containing less than 20 g total fat may produce essential fatty acid deficiency in the infant if supplemental essential fatty acids are not given.

Vitamins

WATER-SOLUBLE VITAMINS.

The vitamin and mineral content of human milk is the standard to which cow's milk and infant formulas are compared (Table 2). The vitamin B₁ (thiamine), vitamin B₂ (riboflavin), and vitamin B₆ (pyridoxine) content of mature human milk is about one fourth that of cow's milk.^29,30 The niacin content of human milk is twice that of cow's milk,^29,30 the folic acid content of human milk is similar to that of cow's milk, but the vitamin B₁₂ (cyanocobalamin) content of human milk is only one sixth that of cow's milk. The human milk content of these vitamins is directly related to the maternal diet. The vitamin C content of human milk depends on maternal diet, and may be five times as high as that of cow's milk.^29,30

TABLE 2. Approximate Nutrient Content of Mature Human Milk, Cow's Milk, and Standard Infant Formula (per deciliter)

Infantile beriberi has been reported when a breast-feeding mother consumes a diet chiefly composed of unfortified, milled grains. Vitamin B₁ supplementation provides prompt resolution.³¹ Deficiencies of vitamin B₂, vitamin B₆, niacin, and folic acid usually are not seen in nursing infants, although supplemental amounts of these vitamins given to malnourished mothers will increase the levels found in human milk.³² The vitamin C content of human milk can be raised by dietary supplement, and seasonal variations in vitamin C content are seen.³² Most healthy mothers consume a diet that meets the recommended daily allowances for water-soluble vitamins. Malnourished and vegan vegetarian mothers require vitamin B₁₂ supplementation to prevent megaloblastic anemia in their infants (Table 1 and Table 3).^33,34

TABLE 3. Recommended Supplements for Maternal Vegetarian Diet

No deficiency syndromes of vitamins A and E have been reported in healthy, term, breast-fed infants.³⁵ Vitamin E-deficient hemolytic anemia has been reported in premature infants and in infants with malabsorption syndromes.³⁶ Supplementation of 25 to 50 IU vitamin E daily usually is given to the infant, although levels of vitamins A and E in human milk can be increased by maternal dietary supplementation.³⁵ Increases in serum vitamin E levels have been reported in newborns whose lactating mothers were using vitamin E oil to treat early nipple tenderness.³⁷ Studies of maternal supplementation have not been performed for significant periods to allow assessment of the potential for toxicity of excessive supplementation.

Rickets has been reported in breast-fed infants, particularly those living in northern climates in winter, in urban areas, and among nonwhites and vegetarians. Daily maternal dietary supplementation of about 10 to 20 μg of vitamin D can prevent rickets in these infants.^38,39

Vitamin K deficiency (hemorrhagic disease of the newborn) is seen primarily in breast-fed infants (or infants receiving formula without supplemental vitamin K) who did not receive vitamin K after delivery.⁴⁰ Fortified infant formula usually contains 50 μg/dl of vitamin K, whereas breast milk only contains 1.5 μg/dl of vitamin K.⁴⁰ Severe deficiency, resulting in massive intracranial hemorrhage, has been reported in several case reports from Taiwan in older breast-fed infants. These infants usually had a preceding gastroenteritis that affected the bacterial flora and its ability to synthesize vitamin K.⁴¹

Minerals

Sodium, potassium, calcium, phosphorus, magnesium, and iron levels in breast milk are unaffected by maternal dietary intake.^35,42 There are reports from 1920 to 1940 of malnourished mothers who nursed and had maternal osteomalacia and tetany.⁴³ There also was one report of increased sodium content in the milk of a mother with cystic fibrosis who was not nursing but who gave an expressed milk sample. This finding may not be valid.⁴⁴ One mother with cystic fibrosis who was actively breast-feeding her infant did not have increased breast milk sodium content.⁴⁵

Iron absorption of breast-fed infants appears to be aided by the higher lactose levels in human milk. Woodruff and associates⁴⁶ found that breast-fed infants had higher serum iron concentrations after birth, and lower total iron-binding capacity at 3, 6, and 9 months of age. Breast-fed infants appear to use dietary iron more efficiently than bottle-fed infants.⁴⁷ Several authors have reported that iron is absorbed in breast-fed infants in sufficient quantities to ensure adequate iron intake for the first 6 to 9 months of life.^48,49 After 6 months of age, as infants show greater interest in chewing, iron-rich solid foods are recommended in the infant's diet.³⁵

Zinc in human milk is more completely absorbed than that in formula, and breast-fed infants have higher serum and hair zinc levels.⁵⁰ The improved bioavailability of zinc in breast milk may prevent clinical zinc deficiency in acrodermatitis enteropathica.⁵⁰ Clinical zinc deficiency also may be seen in breast-fed premature infants with necrotizing enterocolitis or other disorders with extensive small bowel resection or unusually high gastrointestinal losses.⁵¹ Maternal dietary supplements usually do not increase breast milk zinc content sufficiently; thus, additional oral or intravenous zinc must be given to the high-risk infant.^35,51

No relationship between maternal dietary copper and breast milk copper concentration is seen.³⁵ Like zinc, copper deficiency in breast-fed infants usually is confined to those receiving parenteral nutrition and affected with short gut syndrome or prematurity.

The use of iodized salt in the maternal diet may double the level of iodine in human milk, which may prevent iodine deficiency.³⁵

Fluoridation of drinking water is not associated with a major increase in maternal milk fluoride levels.³⁵ Fluoride supplementation, 0.25 to 0.5 mg/day, is recommended for the nursing infant.

The mean selenium concentration of human milk is 2 μg/100 ml, which is about twice that of formula and correlates with the protein content of milk.⁵² There are reports of selenium toxicity in adults living in areas of seleniferous soil. The symptoms included chronic dermatitis, fatigue, and dizziness.⁵² No reports of this syndrome in breast-fed infants have been identified.

Individualization is required to determine when supplementation with formula or solid foods is appropriate. One approach is to compare human milk production with recommended dietary allowances. Recommended daily allowances estimate nutrition requirements based on metabolic balance studies to which a generous safety margin has been added. They may overestimate actual needs. These recommendations do not take into account individual variability and the infant's ability to adjust physiologic efficiency to food availability.

If human milk contains an average of 69 kcal/dl, a child weighing 5 kg at 2 months would need an average of 900 ml/day of breast milk to meet the recommended daily allowance.⁵³ The average amount of breast milk produced in the second month of lactation in American mothers is reported to be 500 to 675 ml/day.¹³ Because most 2-month-old infants grow well on breast milk alone, either the recommended daily allowance is overly generous or the methods for estimating human milk production grossly underestimate the amount produced.

As long as a breast-fed infant is growing appropriately, maternal milk is providing adequate volume, calories, and protein, and the mother's diet is adequate. Currently, infants tend to weigh less and to have decreased triceps skinfold thickness compared with infants born in previous years. This change may reflect a fear of obesity in late life caused by excessive weight in infancy and a subsequent change in feeding habits, including a delay in the introduction of solid foods.⁵⁴ Assessing the adequacy of other nutrients in the breast-fed infant does not vary according to the mode of feeding. A combination of anthropometric measures and clinical symptoms can be used to assess adequacy. Clinical symptoms of specific nutritional deficiencies in the infant are listed in Table 4.

TABLE 4. Clinical Signs of Nutritional Deficiencies in the Infant

Except for vitamin D, routine vitamin and mineral supplementation is not necessary for the healthy, well-nourished breast-feeding mother. Many mothers continue to take their prenatal vitamins after delivery, which is reasonable until the infant is consuming a variety of solid foods in addition to human milk. Clinical signs that suggest maternal deficiencies of selected nutrients are listed in Table 5.

TABLE 5. Clinical Signs of Nutritional Deficiencies in the Mother

Vitamin B₁₂ and calcium supplementation may be necessary if the mother consumes a vegetarian diet.^32,33 Women who are undernourished and eating a diet during pregnancy containing less than 70% of the recommended daily allowances may need a multivitamin and mineral supplement.^32,35

The effects of megavitamin supplementation are unknown. Because increased maternal intake of vitamin A and vitamin D can substantially increase their content in human milk, prolonged excessive maternal vitamin A and vitamin D supplementation has the potential for infant toxicity.³⁵

Excessive vitamin C ingestion in pregnant women has resulted in withdrawal scurvy in their infants.⁵⁵ The vitamin C content of human milk increases within 30 minutes of maternal ingestion.³⁰ Mothers who ingest large doses of vitamin C should taper rather than abruptly stop its ingestion.

Employment

Maternal employment soon after the infant's birth is increasingly common and need not preclude continued breast-feeding. Frequency of breast emptying while away from the infant varies with infant age, maternal discomfort and desire to provide human milk for missed feedings, and availability of facilities for comfortable pumping and appropriate storage of pumped milk.^12,56 Women are likely to breast-feed longer when provision is made for use of an electric breast pump in privacy, with adequate facilities for storage of the milk at work.⁵⁷ Many women substitute one or more formula feedings for breast-feeding instead of pumping and saving milk while at work.

The nutritional needs of the lactating mother will vary with the frequency of her daily nursing periods. One or two missed infant feedings a day probably does not substantially alter the mother's nutritional needs, especially if she is active and has other energy needs. More than two missed feedings will either proportionally reduce the mother's dietary needs or lengthen the time it takes for her to use her pregnancy-acquired fat stores.

Vegetarian Diet

Many lactating women exclude meats or animal products from their diets. The semi-vegetarian (who only avoids red meats) and the ovo-lacto-vegetarian (who eats no flesh foods) are at risk for maternal iron and zinc deficiency.⁵⁸ The lacto-vegetarian (who also avoids eggs) may be at additional risk for protein deficiency without careful selection of complementary proteins.⁵⁸ The vegan (who consumes only vegetables, grains, and fruits) is at high risk for maternal and infant mineral, protein, vitamin D, vitamin B₁₂, and other B vitamin deficiencies.^33,34,58 Recommended supplements for lactating mothers who follow vegetarian diets are listed in Table 3.

Megaloblastic anemia with profound neurologic manifestations has been reported in some infants of vegan mothers. The maternal serum vitamin B₁₂ levels in these cases are marginal to slightly low.^33,34

The zen macrobiotic diet is nutritionally inadequate in almost all required nutrients. It is contraindicated for the pregnant or lactating woman.⁵⁸ Any diet containing high amounts of fiber and whole grain with excessive dietary phytates may impair absorption of iron, zinc, and calcium. The maternal intake may appear to be adequate, but clinical symptoms of iron, zinc, and calcium deficiency in the mother are present.⁵⁸

The fatty acid content in human milk is altered in vegetarian women whose diet meets the recommended daily allowance for all other nutrients.⁵⁹ Long-chain saturated fatty acid levels are reduced, and levels of polyunsaturated fatty acids are increased.⁵⁹ The clinical significance of this effect is unknown.

Diabetes

Mothers with diabetes may breast-feed their infants successfully. Close control of blood glucose levels during pregnancy produces infants with few hypoglycemic and hypocalcemic episodes in the neonatal period.⁶⁰ These infants often are alert and are not likely to have difficulties in breast-feeding or a need for prolonged intravenous administration of glucose and calcium.

Just as with nondiabetic mothers, attention must be paid to increasing the maternal diet by about 500 calories/day to provide for the energy needs for breast milk production.¹⁷ Some of the energy required may be derived from fat stores developed during pregnancy.

Close monitoring of maternal serum glucose levels is recommended to avoid ketonuria and ketonemia that may occur during fat store mobilization. Although most mothers with diabetes experience about a 10% decrease in insulin requirements during lactation, some may require an increase in insulin dosage.⁶¹

Breast-feeding in the immediate postpartum period may be slow to be fully established because infants of some diabetic mothers are delivered before 40 week's gestation. These infants may have hypoglycemia and hypocalcemia, and they may not have a vigorous suck.⁶² A breast pump may be useful to stimulate milk production until the infant can nurse. Because the volume of milk obtained with a mechanical pump often is less than that after established breast-feeding, maternal insulin needs may vary during during this period.

Gastrointestinal Disease

The lactating mother who has gastrointestinal disease resulting in malabsorption may be at risk for nutritional deficiencies. Moderate nutritional depletion is defined as a score of less than 90% on standard parameters of nutritional assessment (including weight for height). Severe depletion is defined as a score of less than 60% of standard parameters.⁶³

Lactating mothers with Crohn's disease, ulcerative colitis, or short gut syndromes (such as following intestinal bypass surgery) must be evaluated for nutritional deficiencies. Loss of weight or an increase in diarrhea may precede other clinical symptoms. These mothers are at risk for decreased absorption of protein, fat and fat-soluble vitamins, and minerals, such as calcium, magnesium, and zinc.⁶⁴

The degree of loss may be quantified by analysis of a 24-hour stool collection. The maternal diet may need to be increased, and some of these women may require chemically defined diets or even total parenteral nutrition. No good studies exist on breast-feeding while the mother is receiving total parenteral nutrition. Breast-feeding would be possible with careful attention to maternal intravenous solution content and nutritional monitoring of the mother and infant.

Phenylketonuria

Several women with classic phenylketonuria (PKU) have reached childbearing age. Many of these women enter pregnancy with elevated serum phenylalanine levels. Several studies have shown a direct correlation between maternal serum phenylalanine level and mental retardation in the otherwise normal fetus, who may or may not have the gene for PKU.^65,66 The current recommendation is that the mother resume her low-phenylalanine diet, using a special low-phenylalanine formula (Lofenalac*) to keep her level of phenylalanine, before and during her pregnancy, less than 5 mg/dl.⁶⁶

Little information exists as to dietary recommendations during lactation for these woman. The mother's milk could be tested periodically for phenylalanine content. If it is significantly higher than the normal range for human milk (29 to 69 mg/dl), then the maternal phenylalanine intake can be adjusted to keep the milk phenylalanine content within the normal range.

Another group of women with hyperphenylalanemia, not classic PKU, has been identified.⁶⁷ These women have borderline to normal intelligence and usually are identified by having a newborn with a transiently positive phenylalanine screen result, a child with unexplained mental retardation, or a relative with mental retardation or PKU.⁶⁷ There is a strong positive correlation between maternal serum phenylalanine level during pregnancy and mental retardation in the offspring.⁶⁸ Dietary recommendations for diet during pregnancy and lactation are the same as for mothers with PKU.

Type I Hyperlipoproteinemia

Of the hyperlipidemias, usually only type I results in a marked change in the fat composition of the milk of the affected lactating mother.⁶⁹ Few case reports are available on lactation in mothers with type I hyperlipidemia.⁶⁹ The fat composition in the milk differs greatly from that in other women's milk. Plasma lipids cannot be taken up by the mammary gland. This inability results in replacement of much of the plasma long-chain fatty acids usually present in breast milk by short- and medium-chain fatty acids synthesized de novo in the mammary gland.⁶⁸ An unaffected nursing infant can synthesize some long-chain fatty acids, but linoleic acid and linolenic acid must be supplied in the infant's diet to prevent essential fatty acid deficiency.⁶⁹

Maternal dietary recommendations include maintaining serum lipid levels within normal limits by following a restricted fat diet, and increasing dietary carbohydrate and protein to provide the additional calories required for lactation. The infant should be monitored for any signs of essential fatty acid deficiency, because it is unknown whether the mother's milk will provide adequate linoleic and linolenic acid.⁶⁹

Cystic Fibrosis

Few case reports are available on lactation in the mother with cystic fibrosis. One brief report described a 20-year-old woman whose breast-fed infant was growing and thriving at 15 weeks after delivery. The mother was unable to maintain her prepartum weight, and her pulmonary status worsened. The sodium content of the breast milk did not differ significantly from the mean values for human milk. The total fat, immunoglobulin (Ig) G, and IgM levels were low, however, and the total protein and IgA levels were elevated. No pathogens were cultured from the milk.⁴⁵

Prematurity

The nutritional needs of the preterm infant differ from those of the term infant. The premature infant has increased requirements for protein, calories, and minerals, particularly calcium and phosphorus, to grow at the same rate as in utero.⁷⁰ The immaturity of these infants may cause problems such as malabsorption, poor suck and swallow reflexes, and necrotizing enterocolitis.⁷⁰

The estimated in utero accretion requirements for sodium, protein, chloride, and potassium may not always be met by human milk alone. Calcium, phosphorus, and magnesium requirements are not met by human milk.⁷¹ Commercially available breast milk fortifiers (Human Milk Fortifier* and Natural Care^†) are available to add to breast milk.

In the infant weighing less than 1200 g, the addition of a fortifier provides milk that more closely meets the infant's nutritional needs.⁷² The amount of breast milk produced may not be adequate because of the infant's poor suck reflex, infrequent breast stimulation by the infant, and maternal anxiety about the infant.⁷⁰ Frequent, consistent pumping or hand expression may be useful in maintaining the maternal milk supply. Metoclopramide 10 mg orally every 8 hours increases milk production.⁷³ It also increases prolactin levels through a dopamine antagonist mechanism.

Milk produced by mothers of premature infants in the first few weeks after birth differs from the milk they produce later and from the milk produced by mothers of term infants.⁷⁴ The initial milk of mothers of premature infants born before 31 week's gestation, more closely meets the infant's needs because it is higher in protein, sodium, fatty acids, and energy.⁷⁵

The well-nourished mother of a premature infant should follow a dietary plan based on recommended dietary allowances for lactation. Maternal anxiety may be high, and additional emotional support often is needed. With time, practice, and emotional support, mothers of premature infants often provide for most, if not all, of their infant's nutritional needs.

Multiple Births

Successful breast-feeding of twins or triplets is possible. The maternal diet should be increased by at least 800 calories/day, and continuation of prenatal vitamins or multivitamins is advised.¹⁷ Mothers of twins or triplets who do not ingest sufficient calories for the extra energy needed for milk production may have increased mobilization of endogenous fat stores and earlier return to prepregnancy weight.⁷⁶

Many twins or triplets are born prematurely and spend time in the newborn intensive care unit. In addition to information and support, breast pumping is recommended to stimulate and maintain milk production until the infants can use some or all of the mother's milk.

Food Allergies

Heredity plays an important role in food allergies and atopic disease. Either skin manifestations of atopia or gastrointestinal symptoms may be related to food allergies. Several studies have attempted to evaluate the prevention of development of infant atopia and gastrointestinal disturbances by manipulating the maternal diet during pregnancy and lactation and by feeding the infant either breast or soy milk.

Several studies of reduction in atopic symptoms differ concerning the value of avoiding allergenic foods in the maternal diet during pregnancy and lactation.⁷⁷ Many of these studies were not well designed and did not control for duration of exclusive breast-feeding.

Other studies suggested a decrease in the infant's gastrointestinal symptoms with a maternal diet devoid of cow's milk and egg proteins. Cow's milk, goat's milk, soy milk, and egg proteins in the maternal diet are secreted into the breast milk.^78,79,80 Jacobsson and colleagues⁸¹ reported high levels of β-lactoglobulin in the milk of mothers whose infants had colic. After cow's milk was removed from the diet, the β-lactoglobulin levels were not detectable, and the colic resolved.

In addition to allergic problems with protein components of cow's milk, lactose intolerance in the mother is prevalent worldwide.⁸² More than 80% of Oriental and Eskimo adults and 60% to 80% of Native Americans, blacks, and Hispanics are lactose intolerant.⁸² Alternative sources of calcium, such as yogurt, cheese, calcium-rich vegetables, and supplemental calcium tablets, are recommended in the maternal diet during pregnancy and lactation.

Current recommendations are to identify high-risk families with an existing atopic child or a mother with documented IgE reactivity. Cow's milk, eggs, nuts, and atopic foods causing IgE reactivity should be avoided during the last trimester of pregnancy (when maternal-fetal transfusion is most common, resulting in the development of infant IgM antibodies) and for the duration of lactation. Supplemental calcium 1000 to 1200 mg/day is required.⁸²

The infant is then either breast-fed or given a casein hydrolysate formula (Nutramigen or Pregestimil*). If there is not a strong family history of soy allergy, soy protein products may be used in the maternal diet during pregnancy and lactation, with additional vitamin B₁₂ supplementation.⁸³

Inborn Errors of Metabolism

PHENYLKETONURIA.

Phenylketonuria is a common inborn error of metabolism, occurring in 1:10,000 white children.⁸⁴ Breast-feeding often was discouraged in the past, and the infant was fed a combination of a small, measured amount of standard formula and a special formula containing low levels of phenylalanine (Lofenalac).⁸⁵ Human milk averages 41 mg/dl phenylalanine, compared with 75 mg/dl in standard infant formulas and 159 mg/dl in cow's milk.⁸⁵ With close monitoring, breast-feeding may be continued for the infant with PKU.

A booklet entitled Guide to Breastfeeding the Infant with PKU^† describes protocols that include weighing the infant before and after feeding, offering Lofenalac after a certain number of minutes at the breast, checking daily blood levels of phenylalanine until the infant's level is stable, substituting Lofenalac for one or two feedings a day and pumping milk at the feeding time to maintain the maternal milk supply, and placing Lofenalac in a nursing supplementer. The supplementer allows the infant to nurse and receive the Lofenalac simultaneously. The optimal blood level of serum phenylalanine that maintains adequate infant growth is 5 to 10 mg/dl.⁸⁵

Other than following the recommended daily allowances for lactation, no alteration in maternal diet is necessary for nursing an infant with PKU. Restricting the intake of maternal dietary protein does not lower the phenylalanine content of breast milk.

TYPE I HYPERLIPOPROTEINEMIA.

This rare metabolic defect is associated with a defect of lipoprotein lipase activity. This defect results in an inability to clear any dietary fat, and levels of serum chylomicrons and serum triglycerides can be as high as 10,000 mg/dl.⁸⁶ The infant's diet usually is restricted to less than 20 g total dietary fat, with added protein and carbohydrate for required kilocalories.⁸⁶

The average fat content of 24-hour pooled milk samples varies from 2.10% to 3.33%.^26,27 At 3% fat content, the infant could be fed a maximum of 660 ml or 22 oz of human milk each day. The remainder of the intake would need to come from a nonfat formula. Each infant must be managed on an individual basis, depending on the fat content of the mother's milk and the feeding technique. The infant could be allowed to nurse for a specific period, and triglyceride levels could be obtained frequently, with nursing time adjusted accordingly. Another alternative, although cumbersome, is to pump the breast and give a measured amount of human milk fortified with nonfat dry milk and another carbohydrate source to the infant in a bottle. The infant requires careful monitoring for any symptoms of linoleic acid deficiency.

CYSTIC FIBROSIS.

Cystic fibrosis is a common inherited enzyme defect, occurring in 1:1500 to 1:2000 live, white births. Eighty-five percent of affected infants have some pancreatic impairment. Regardless of the feeding method, these infants usually need supplemental fat-soluble vitamins (aqueous preparations of vitamins A, E, D, and K) and exogenous pancreatic enzymes.⁸⁶

Drugs and Chemicals in Breast Milk

To alter the practice of weaning as a precaution during drug therapy, information must be available to permit accurate evaluation of the risks and benefits of therapy to the mother and infant. Older studies often were contradictory, with most human data including only a small number of subjects or a single case report. Single determinations of a drug in breast milk are of limited value. Only within the last 10 years have sound pharmacokinetic principles been applied to drug or chemical excretion in human breast milk. Most drugs in breast milk are found in concentrations equal to or lower than maternal plasma levels.

Many important drugs have not been studied adequately, and information regarding their short-term or long-term effects in infants often is lacking. When publishing data, manufacturers sometimes use such words as may or might when referring to the possible effect of the drug on the nursing infant. Often, these words are understood to mean that the drug is contraindicated in nursing mothers. Neonatal effects are thought to be negligible with antibiotic exposure, except for allergic sensitization, candidal infection, or diarrhea. Cardiovascular drugs do not cause adverse effects on the newborn at maternal therapeutic doses. Gastrointestinal drugs may cause diarrhea or colic. Effects from exposure to psychoactive substances in breast milk are unknown, but may be of concern. Long-term antihistamine use may cause sedation or decreased feeding. Concentrations of hormones and synthetic substances are thought to be too small to be clinically significant. Information about specific drugs may be found in standard textbooks.^87,88

Volatile oils, such as in garlic, onion, and melons, are poorly tolerated by the infant.⁵⁸ Artificial colors and dyes used in beverages, gelatin desserts, and other foods can color the milk.⁸⁹ Lawrence⁵⁸ reported cases of green milk caused by a sports drink colored with food dye, kelp, seaweed, and colored vitamin tablets. Such color changes do not affect the nutritional content of the milk. Excessive maternal consumption of caffeine and methylxanthines (several cups of coffee or tea each day) causes hyperstimulation in the nursing infant.⁹⁰ Herbal teas may contain natural coumarins or other potent pharmacologic and psychogenic compounds that could cause bleeding or other problems.⁹¹ It is not known whether significant amounts of these compounds are secreted into human milk in women who drink herbal teas regularly.

Women with a high exposure to agricultural chemicals, such as polychlorinated biphenyl (PCB), may have blood levels 10 to 100 times those of nonexposed mothers.⁹² Detectable levels in their milk usually are lower than the levels found in cow's milk. The breast-fed infants of these mothers have PCB residue in the blood. Levels in the infant relate directly to the duration of breast-feeding rather than to maternal serum PCB concentration.⁹² No significant medical problems in these infants have been seen, and no infants were diagnosed with chronic PCB poisoning. Testing of human milk for PCB content is not required or recommended unless there has been an unusually high exposure or the area has been designated by the state health department as heavily contaminated.

Often, questions are asked about the suitability of breast milk in meeting the infant's nutritional needs under a variety of infant and maternal conditions. The following situations may result in temporary or complete discontinuation of breast-feeding.

Cancer of the Breast

If breast-feeding means that the mother may delay definitive treatment, it is not recommended. A positive family history for breast cancer is not a contraindication to breast-feeding.⁹³

Other Cancer

During chemotherapy, other than that with prednisone, the mother's milk may be pumped and discarded for the duration of chemotherapy. Breast-feeding can be resumed after drug levels no longer are found in the milk, or until the time since the last dose exceeds four half-lives of the drug.

Tuberculosis

Sputum-positive tuberculosis is a contraindication to breast-feeding until the mother is under effective treatment for at least 1 week and the infant is receiving isoniazid prophylaxis.⁹⁴ Milk may be pumped and discarded until this time.

Hepatitis B

Hepatitis B can be transmitted to the infant transplacentally during pregnancy, by the fecal-oral route during delivery, and through breast milk.^94,95,96 For mothers who have active hepatitis B during pregnancy or those who are asymptomatic carriers, the American Academy of Pediatrics Committee on Infectious Disease has taken the position that “breastfeeding should be avoided if artificial milk formulas and adequate refrigeration facilities are available. However, breastfeeding is indicated for infants living in areas of the world where hepatitis, type B, infection is highly endemic and artificial formulas and refrigeration are not available.”⁹⁴

Other authors have not found hepatitis B in unconcentrated breast milk specimens from women who were carriers but were not actively infected.^95,96 Krugman⁹⁷ noted that the use of vaccines against viral hepatitis so substantially reduced its incidence that the risk associated with breast-feeding by carrier mothers may be significantly less than previously thought.

Herpes Simplex

Fatal newborn cases of herpes simplex type 1 and herpes simplex type 2 involving maternal breast lesions have been reported.^98,99 If suspicious breast lesions are present, the mother should empty her breasts and discard the milk until cultures of the lesions and the expressed milk have been evaluated.

Acquired Immune Deficiency Syndrome Virus

Case studies report possible transmission of acquired immune deficiency syndrome retrovirus through human milk.^100,101 Women in high-risk groups (e.g., intravenous drug abusers, those born in areas of high incidence of heterosexual transmission, those who have been sexual partners of affected men) should be excluded from donating human milk. Seropositive women should be advised against breast-feeding their newborns.

Radioactive Drugs

Interruption of breast-feeding is necessary during exposure to diagnostic radioactive isotopes. Milk should be pumped and discarded during the first four half-lives of the drug. For sodium pertechnetate technetium 99m, iodohippurate sodium iodine 131, and similar compounds, the infant should be fed immediately before the administration of the radionuclide. The next three milk fractions should be discarded before nursing is resumed.¹⁰² Only the first milk fraction after radionuclide administration should be discarded for red blood cell labeled (technetium 99m), petetic acid (technetium 99m), methylene diphosphonate (technetium 99m), and edetic acid (chromium 57).^102,103

When radionuclide compounds are used for treatment, breast milk also should be discarded for four half-lives. For iodine 131, discarding milk for four half-lives (half-life of 8 days) causes a 4-week interruption of breast-feeding.¹⁰⁴

Oral Contraceptives

The advisability of recommending oral contraceptives to lactating women continues to be debated, both for their maternal and infant effects. Lonnerdal and associates¹⁰⁵ reported significant differences in some protein components of human milk and a decrease in total volume among women taking oral contraceptives compared with women not using oral contraceptives.¹⁰⁶ However, even with these differences, nutrient composition of the breast milk was within normal limits, and no infants had clinical signs or nutritional deficiencies.

Stefan and Nygren¹⁰⁶ reported that concentrations of ethinyl estradiol in breast milk obtained from women taking oral contraceptives were approximately 1% of the dose taken. They estimated that an oral contraceptive containing 50 μg of ethinyl estradiol excretes 10 ng of ethinyl estradiol per 600 ml breast milk expressed.

Roepke and Kirksey¹⁰⁷ found that women who took oral contraceptives for longer than 30 months before their pregnancy had substantially reduced reserves of vitamin B₆ during pregnancy and lactation. Some authors suggest that supplemental vitamin B₆ be given during pregnancy to women with a history of long-term use of oral contraceptives.¹⁰⁷

Infant Galactosemia

Galactosemia is an absolute contraindication to breast-feeding because the chief carbohydrate source in milk is lactose. Galactosemia occurs in only 1:60,000 live births.¹⁰⁸ Use of human or cow's milk or other products containing lactose will result in hepatomegaly, jaundice, cataract formation, and mental retardation in the infant. Meat base or casein hydrolysate formulas are used to meet nutritional requirements.⁸⁶

Most women who are delivered of an infant have adequate nutritional stores for breast-feeding. The maternal diet can influence the nutrient content of breast milk, particularly the volume of milk produced, its protein content, its water-soluble vitamin content, and its fatty acid composition.

Vitamin and mineral supplementation of the maternal diet usually is not necessary, except for the strict vegetarian or malnourished mother. Special situations, such as diabetes, gastrointestinal problems, and inborn errors of metabolism, do not preclude breast-feeding if recommended adjustments to the maternal diet are made. The nutritional needs of infants with special problems may be partially or fully met by breast-feeding. Specific adjustments to the maternal or infant diet may be required.

Many chemicals and drugs are excreted into breast milk. Seldom is breast-feeding contraindicated because of drugs or environmental contaminants, although an awareness of potential effects may make the mother avoid unnecessary exposure to these substances. Breast-feeding may have to be suspended temporarily when certain radionuclides are used for diagnosis or treatment, or while the mother is receiving chemotherapy. Afterward, it may be resumed.

Infectious agents, such as those of hepatitis, herpes, tuberculosis, or acquired immune deficiency syndrome, may be transmitted to the infant through breast milk. Temporary or permanent cessation of breast-feeding may be recommended. The only absolute contraindication to breast-feeding is galactosemia in the infant.

Special maternal or infant needs requiring dietary changes on either part sometimes are used as reasons to discourage breast-feeding. For a motivated mother who wants to nurse her infant, the specific recommendations in this chapter are designed to help her to provide for both her own and her infant's nutritional needs. These recommendations were intended to be used to promote rather than discourage breast-feeding.

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33. Higginbottom MC, Sweetman L, Nyhan WL: A syndrome of methylmalonic aciduria, homocystinuria, megaloblastic anemia and neurologic abnormalities in a vitamin B₁₂ -deficient breast-fed infant of a strict vegetarian. N Engl J Med 299: 317, 1978

34. Johnson RP, Roloff JS: Vitamin B₁₂ deficiency in an infant strictly breast-fed by a mother with latent pernicious anemia. J Pediatr 100: 917, 1982

35. American Academy of Pediatrics Committee on Nutrition: Nutrition and lactation. Pediatrics 68:435, 1981

36. Ziegler EE, Biga RL, Fomon SJ: Nutritional requirements of the premature infant. In Suskind RM (ed): Textbook of Pediatric Nutrition. New York, Raven Press, 1981

37. Marx CM, Izquierdo A, Driscoll JW et al: Vitamin E concentrations in serum of newborn infants after topical use of vitamin E by nursing mothers. Am J Obstet Gynecol 152: 668, 1985

38. Edidin DV, Levitsky LL, Schey W et al: Resurgence of nutritional rickets associated with breast-feeding and special dietary practices. Pediatrics 65: 232, 1980

39. Ala-Houhala M: 25-Hydroxy-vitamin D levels during breast-feeding with or without maternal or infantile supplementation of vitamin D. J Pediatr Gastroenterol Nutr 4: 220, 1985

40. Lane PA, Hathaway WE: Vitamin K in infancy. J Pediatr 106: 351, 1985

41. Chaou WT, Chou ML, Eitzman DV: Intracranial hemorrhage and vitamin K deficiency in early infancy. J Pediatr 105: 880, 1984

42. Greer FR, Tsang RC, Levin RS et al: Increasing serum calcium and magnesium concentrations in breast-fed infants: Longitudinal studies of minerals in human milk and in sera of nursing mothers and their infants. J Pediatr 100: 59, 1982

43. Anderson AB, Brown A: Tetany following prolonged lactation on a deficient diet. Lancet II:482, 1941

44. Whitelaw A, Butterfield A: High breastmilk sodium in cystic fibrosis. Lancet II:1288, 1977

45. Welch MJ, Phelps DL, Osher AB: Breast-feeding by a mother with cystic fibrosis. Pediatrics 67: 664, 1981

46. Woodruff CW, Latham C, McDavid S: Iron nutrition in the breast-fed infant. J Pediatr 90: 36, 1977

47. McMillan JA, Landau SA, Oski FA: Iron sufficiency in breast-fed infants and the availability of iron from human milk. Pediatrics 58: 686, 1976

48. Siimes MA, Salmenpera L, Perheentupa J: Exclusive breast-feeding for nine months: Risk of iron deficiency. J Pediatr 104: 196, 1984

49. Duncan B, Schifman RB, Corrigan JJ et al: Iron and the exclusively breast-fed infant from birth through six months. J Pediatr Gastroenterol Nutr 4: 421, 1985

50. Sandstrom B, Cederblad A, Lonnerdal B: Zinc absorption from human milk, cow's milk and infant formulas. Am J Dis Child 137: 726, 1983

51. Ziegler EE: Infants of low birth weight: Special needs and problems. Am J Clin Nutr 41: 440, 1985

52. Smith AM, Picciano MF, Milner JA: Selenium intakes and status of human milk and formula fed infants. Am J Clin Nutr 35: 521, 1982

53. Whitehead RG: Infant physiology, nutritional requirements and lactational adequacy. Am J Clin Nutr 41: 447, 1985

54. Salmenpera L, Perheentupa J, Siimes MA: Exclusively breast-fed infants grow slower than reference infants. Pediatr Res 19: 307, 1985

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56. Frederick IB, Auerbach KG: Maternal-infant separation and breast-feeding: The return to work or school. J Reprod Med 30: 523, 1985

57. Katcher AL, Lanese MG: Breast-feeding by employed mothers: A reasonable accommodation in the work place. Pediatrics 75: 644, 1985

58. Lawrence RA: Breastfeeding: A Guide for the Medical Profession, 2nd ed. St Louis, CV Mosby, 1985

59. Finley DA, Lonnerdal B, Dewey KG et al: Breast milk composition: Fat content and fatty acid composition in vegetarians and nonvegetarians. Am J Clin Nutr 41: 787, 1985

60. Freinkel N, Dooley SL, Metzger BE: Care of the pregnant woman with insulin-dependent diabetes mellitus. N Engl J Med 313: 96, 1985

61. Miller DL: The diabetic nursing mother. Keeping Abreast J 1: 102, 1976

62. Lubchenco LO: Infants of diabetic mothers. Keeping Abreast J 1: 107, 1976

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65. Lenke RR, Levy HL: Maternal phenylketonuria: Results of dietary therapy. Am J Obstet Gynecol 143: 548, 1982

66. Acosta PB, Blaskovics M, Cloud H et al: Nutrition in pregnancy of women with hyperphenylalaninemia. J Am Dietetic Assoc 80: 443, 1982

67. Lipson A, Buehler B, Badley J et al: Maternal hyperphenylalaninemia: Fetal effects. J Pediatr 104: 216, 1984

68. Levy HL, Waisbren SE: Effects of untreated maternal phenylketonuria and hyperphenylalaninemia on the fetus. N Engl J Med 309: 1269, 1983

69. Myher JJ, Kuksis A, Steiner G: Milk fat structure of a patient with type I hyperlipidemia. Lipids 19: 673, 1984

70. American Academy of Pediatrics Committee on Nutrition: Nutritional needs of low birthweight infants. Pediatrics 60:519, 1977

71. Nutrition Committee of the Canadian Paediatric Society and the Committee on Nutrition of the American Academy of Pediatrics: Breastfeeding. Pediatrics 62:591, 1978

72. Schanler RJ, Garza C, Nichols BL: Calcium (Ca) and phosphorus (P) balance in very low birthweight infants (VLBW) fed fortified human milk (FHM) (abstr). Pediatr Res 17: 200A, 1983

73. Ehrenkranz RA, Ackerman BA: Metoclopramide effect on faltering milk production by mothers of premature infants. Pediatrics 78: 614, 1986

74. Schanler RJ, Oh W: Composition of breast milk obtained from mothers of premature infants as compared to breast milk obtained from donors. J Pediatr 96: 679, 1980

75. Lepage G, Collet S, Bougle D et al: The composition of preterm milk in relation to the degree of prematurity. Am J Clin Nutr 40: 1042, 1984

76. Addy HA: The breastfeeding of twins. Environ Child Health 21: 231, 1975

77. Kramer MS, Moroz B: Do breast-feeding and delayed introduction of solid foods protect against subsequent atopic eczema? J Pediatr 98: 546, 1981

78. Kilshaw PJ, Cant AJ: The passage of maternal dietary proteins into human breast milk. Int Arch Allergy Appl Immunol 75: 8, 1984

79. Cant AJ, Bailes JA, Marsden RA: Cow's milk, soya milk and goat's milk in a mother's diet causing eczema and diarrhoea in her breast-fed infant. Acta Paediatr Scand 74: 467, 1985

80. Cant AJ, Marsden RA, Kilshaw PJ: Egg and cow's milk hypersensitivity in exclusively breast-fed infants with eczema and detection of egg protein in breast milk. Br Med J 291: 932, 1985

81. Jacobsson I, Lindberg T, Benediktsson B et al: Dietary bovine β-lactoglobulin is transferred to human milk. Acta Paediatr Scand 74:342 1985

82. National Dairy Council: Perspective on milk intolerance. Dairy Council Dig 49:31, 1978

83. Hamburger RN, Heller S, Mellon MH et al: Current status of the clinical and imunologic consequences of a prototype allergic disease prevention program. Ann Allergy 51: 281, 1983

84. Scriver CR, Clow CL: Phenylketonuria: Epitome of human biochemical genetics. N Engl J Med 303: 1336, 1980

85. Ernest AE, McCabe ER, Neifert MR et al: Guide to Breastfeeding the Infant with PKU. Washington DC, US Government Printing Office, 1980

86. American Academy of Pediatrics: Pediatric Nutrition Handbook. Evanston, IL, American Academy of Pediatrics, 1979

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89. Roseman BD: Letter: Sun kissed urine. Pediatrics 67: 443, 1981

90. American Academy of Pediatrics Committee on Drugs: The transfer of drugs and other chemicals into human breast milk. Pediatrics 72:375, 1983

91. Siegel RK: Herbal intoxication: Psychoactive effects from herbal cigarettes, tea, and capsules. JAMA 236: 473, 1976

92. Yakushiji T, Watanabe I, Kuwabara K et al: Postnatal transfer of PCB's from exposed mothers to their babies: Influence of breast-feeding. Arch Environ Health 39: 368, 1984

93. Byers T, Graham S, Rzepka T et al: Lactation and breast cancer. Am J Epidemiol 121: 664, 1985

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95. Beasley RP, Stevens CE, Shiao IS: Breast-feeding and hepatitis B. Lancet II:1089, 1975

96. DeMartino M, Appendino C, Resti M et al: Should hepatitis B surface antigen positive mothers breast-feed? Arch Dis Child 60: 972, 1985

97. Krugman S: Viral hepatitis: 1985 update. Pediatr Rev 7: 3, 1985

98. Dunkle L, Schmidt RR, O'Connor DM: Neonatal herpes simplex infection possibly acquired via maternal breast milk. Pediatrics 63: 250, 1979

99. Quinn PT, Lofbera JV: Maternal herpetic breast infection: Another hazard of neonatal herpes simplex. Med J Aust 2: 411, 1978

100. Thiry L, Sprecher-Goldberger S, Jonckheer T et al: Isolation of AIDS virus from cell-free breast milk of three healthy virus carriers. Lancet II:891, 1985

101. Ziegler JB, Cooper PA, Johnson RO et al: Postnatal transmission of AIDS-associated retrovirus from mother to infant. Lancet I:896: 97, 1985

102. Mountford PJ, Coakley AJ: Excretion of radioactivity in breast milk after an indium-111 leukocyte scan. J Nucl Med 26: 1096, 1985

103. Ahlgren L, Ivarsson S, Johannson L et al: Excretion of radionuclides in human breast milk after the administration of radiopharmaceuticals. J Nucl Med 26: 1085, 1985

104. Coakley AJ, Mountford PJ: Nuclear medicine and the nursing mother. Br Med J 291: 159, 1985

105. Lonnerdal B, Fordum E, Hambreaus L: Effect of oral contraceptives on composition and volume of breast milk. Am J Clin Nutr 33: 816, 1980

106. Stefan N, Nygren KG: Transfer of contraceptive steroids to human milk. Res Reprod 11: 1, 1979

107. Roepke JLB, Kirksey A: Vitamin B₆ nutriture during pregnancy and lactation: The effect of long term use of oral contraceptives. Am J Clin Nutr 32: 2257, 1979

108. Berger LR: Commentary: When should one discourage breast-feeding. Pediatrics 67: 300, 1981