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1 ~ Dietary Intake During Pregnancy Since nutrient supplementation of healthy pregnant women is necessary only when the usual intake of nutrients from the diet is insufficient to meet physiologic requirements (see Chapter 12), in this chapter the subcommittee reviews data on the usual dietary intake of nutrients by pregnant women and identifies nutrients that are frequently consumed below the recommended levels. The subcommittee noted that if a population group were to consume, on average, less of a nutrient than the Recommended Dietary Allowance (RDA) (NRC, 1989), this would not necessarily imply that they are deficient in that nutrient. It may, however, mean that some individuals within the group are at risk of deficiency. AVAILABLE DIETARY DATA The following review of data on nutrient intakes during pregnancy is restricted to women residing in the United States. Lack of data prevented the inclusion of some essential nutrients, and certain others were excluded (e.g., phosphorus) because adequacy of intake has been well established. Limited data on the nutrients omitted from Able 13-1 are provided in Chapters 15, 17, and 18. All reports published since 1978 were selected if they included data for energy and at least four nutrients. That year was selected as a cutoff point because older data are unlikely to be representa- tive of current nutrient intakes for several reasons. For example, advice to restrict weight gain during pregnancy by reducing food intake is given less frequently than it was in the past. Furthermore, estimates of the nutrient 258

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DIETARY INTAKE 259 composition of foods have been revised. Thus, nutrient data bases have changed accordingly over time and have become more complete. There have also been changes in the types of foods available to and consumed by the U.S. public, and in the 1980s, the food intake of increasing numbers of pregnant women was affected by their participation in the Special Sup- plemental Food Program for Women, Infants, and Children (WIC) (see Chapter 3, Figure 3-5~. Table 13-1 summarizes the references from which data were abstracted; provides the year of each report; and notes the population groups studied, the stage of pregnancy at which intake was measured, the dietary data collection method, and the number of days that intake was measured. LIMITATIONS OF THE DATA Neither the National Health and Nutrition Examination Surveys (NHANES), the Nationwide Food Consumption Surveys (NFCS), nor the Continuing Survey of Food Intake by Individuals (CSFII) selves as a source of representative dietary data for pregnant women in the United States. Since the number of pregnant women included in the surveys is small, e.g., 116 of 2,910 women in the first wave of CSFII in 1985 (USDA, 1985), valid comparisons cannot be made across age, ethnic, or socioeconomic groups. However, results from one analysis of CSFII data on pregnant women are included in Able 13-2. Low-income women were heavily represented in the recent dietary intake studies (at least 8 of the 11 studies) of pregnant women included in Table 13-2. That is, many studies were conducted with WIC participants, whose family income is less than 185% of the national poverty level. This factor, combined with the small sample size of most studies, introduces some uncertainty regarding the extent to which the data can be generalized to the ethnic and age groups specified in Tables 13-1 and 13-2. Differences between studies make it difficult to compare their results. Although most investigators used a 24-hour diet recall method to obtain the dietary data, the accuracy of the food intake information must have varied with the level of training of the interviewers, the use of food models, the time available for the interview, characteristics of the subjects such as their education level and economic status, and the sensitivity and knowledge of interviewers concerning cultural food patterns. In the studies in which women were asked to record or to record and weigh their intake, it is likely that some women changed their food intake because of the need to keep a record. Different investigators used different nutrient data bases, which vary in completeness and accuracy (Dwyer and Suitor, 1984~. This is especially likely to affect estimates of the intakes of such nutrients as folacin, vitamin Be, and zinc.

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264 DIETARY INTAKE AND NUTRIENT SUPPLEMENTS In 1988, approximately 523,000 pregnant women per month were par- ticipants in WIC (J. Hirshman, Food and Nutrition Service, personal com- munication, 1988~. Several investigators (see Table 13-1) did not identify the proportion of their subjects who were enrolled in WIC or separate the dietary intake data of participants from those of nonparticipants. Nutrient intakes by women from lower socioeconomic groups may be increased by participation in this program, as described later in this chapter. Information on the effects of pregnancy on food choices and patterns, diet quality, and nutrient intake in the United States is virtually nonexistent. Since 1978, no investigator in the United States has made a systematic study of intake before and throughout pregnancy in the same women. With two exceptions (Endres et al., 1985; S. Murphy and B. Abrams, University of California at Berkeley, personal communication, 1988), no comparisons were made between nonpregnant and pregnant women. It is unclear whether or how appetite changes during pregnancy. Data on intakes during the first trimester are scarce because most women make no more than one prenatal visit during this time. (In 1985, 18.1% of the pregnant women in the United States received no prenatal care in the first trimester. For teenagers and black women, first-trimester prenatal care was even less common [IOM, 1988~.) In the few early studies in which appetite was investigated, some women reported that their appetite was greater, whereas others reported no difference (see review by Taggart, 1961~. Beat (1971) reported that appetite decreased in the first trimester, improved in the fifth month, and declined thereafter. Nausea during early pregnancy was reported by about half of the pregnant women studied by Brandes (1967~. It is not known how nausea and vomiting affect the daily amount and nutritional quality of food con- sumed, but these unpleasant conditions have been associated with favorable pregnancy outcomes (Brandes, 1967; Klebanoff et al., 1985; Tierson et al., 1986~. The few attempts to investigate whether maternal diet contributes to nausea or vomiting have failed to find a relationship. The lack of evidence that vitamin Be supplements help relieve nausea is discussed in Chapter 18. Food-related behaviors that change more often during pregnancy than at any other stage of life include cravings, aversions to specific foods, and pica (the ingestion of nonfood substances such as laundry starch) (NRC, 1982~. In one study of married pregnant women of northern European background from middle- and upper-income groups in the United States, 76% reported a craving for at least one food item, and 85% reported aversion to at least one (Tierson et al., 1985~. These cravings and aversions had predictable effects on the amounts of the specific foods consumed, but it was not possible to generalize about the overall nutritional impact because of the large number and variety of foods involved. In another study of a random sample of 463 women who had recently delivered babies, more

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DIETARY INTAKE 265 than 90% reported a craving for at least one food item during their last trimester of pregnancy, and more than 50% reported aversion to at least one (Worthington-Roberts et al., 1989~. NUTRIENT INTAKES OF PREGNANT WOMEN Nutrient intake data from studies of pregnant women during the 1980s are summarized in Table 13-2. Average intakes reported to be lower than the 1989 RDAs for pregnant women are set in boldface type. The RDAs for protein, vitamins, and minerals provide a substantial margin of safety and exceed the requirements of almost all individuals in a specific population group. For example, approximately 50% of the population has an adequate intake of a nutrient at >77% of the RDA, and 97.5% has an adequate intake at 100% of the RDA, assuming that the RDAs are 30% (about 2 standard deviations) higher than the mean requirement of the population. The following generalizations can be made about the data presented in Table 13-2: The nutrient intake by pregnant women in the United States has been measured in relatively few studies during the last decade. Information is particularly sparse on adult women of northern European descent. Reported mean daily energy intakes varied markedly, ranging from approximately 1,500 to 2,800 kcal. The extent to which this reflects dif- ferences in data collection techniques (and consequently over- or underre- porting of food intake) or differences in age, body size, or activity level is not clear. Not surprisingly, with a few exceptions, mean nutrient intakes by the groups tended to rise or fall with the reported energy intake. On average, intakes of protein, riboflavin, vitamin Bit, and niacin exceeded the RDAs, and there was only one report of low vitamin C intake. This exception (Brennan et al., 1983a,b) was for the chemically analyzed vitamin C content of the foods consumed, which was substantially lower than that calculated from food composition tables. Average thiamin intakes were close to the RDA in all studies. Some nutrients were consumed consistently in amounts substan- tially less than the RDA. These include vitamins Be, D, E, and folacin; . . . iron; zinc; an' magnesium. Mean calcium intake was less than the RDA in all but one study, in which high intakes of all nutrients were reported for a group of teenagers (Lords et al., 1985), and very close to the RDA in another study (Suitor et al., 1989~. Calcium values shown in Able 13-2 were especially low for nonparticipants in WIC (Rush et al., 1988), black women (Brennan et al., 1983a), and Navajo women (Butte et al., 1981~. .

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266 DIETARY INTAKE AND NUTRIENT SUPPLEMENTS In the few studies that included vitamin E, intake averaged about half of the RDA for women of Hispanic and Navajo origin but was some- what higher for others. The few studies including vitamin D indicated that intake of that vitamin was approximately half the RDA There was a wide range in mean nutrient intake across different samples of pregnant teenagers. One group of investigators (Endres et al., 1985, 1987) found that the quantity and quality of the diet consumed by pregnant adolescents was similar to that consumed by pregnant adults. In contrast, Loris et al. (1985) observed higher intakes of energy and most other nutrients among adolescents as well as a greater weight gain than is typical for adults. Adolescents receiving more nutrition education consumed greater amounts of energy-400 kcaVday on average more than did those with little nutrition education. . Some of the food composition data bases lacked information on nutrients that may be present in the diets of pregnant women at levels that are substantially less than recommended. This may partially explain why many of the investigators did not present values for zinc; magnesium; copper; and vitamins Be, Bit, D, and E. The mean daily consumption of iron from foods ranged from 10.3 to 16.6 ma. The highest iron intakes were reported for black and Navajo women. However, comparisons of adequacy of iron intake were not made based on the amount of available iron (see Chapter 144. Vitamin A intakes were reported in international units (IUs) or in milligrams, whereas the RDAs are given as micrograms of retinal equiv- alents (REs). The subcommittee converted intake data to micrograms of RE based on the assumption that 1 RE is equivalent to 5 IU of vitamin A obtained from the typical U.S. diet in the form of retinal (from animal products) and carotenoids (from plants) (Olson, 1987) and that 1 mg of retinal equals 3,333 IU. Mean intakes of this vitamin appeared to be close to the RDA, on average, but were low in pregnant Navajo women. In summary, the data in Table 13-2 indicate that, on average, pregnant women in the studies cited probably met their RDA for protein, thiamin, riboflavin, niacin, and vitamins A' Bit, and C. They were less likely to have met their RDAs for vitamins Be, D, E, and folacin; iron; calcium; zinc; and magnesium. Because the RDA for iron during pregnancy is more than twice as high as average intake, it cannot be met from dietary sources without the use of highly fortified foods or very careful food selection (see Chapter 14~. The fact that the average intake of eight nutrients by almost all groups studied was substantially below the RDAs for pregnant women should be interpreted with caution. The RDAs for all vitamins and minerals include a safety factor to cover the needs of even those healthy individuals whose

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DIETARY INTAKE 267 metabolism is such that their requirements are especially high; thus, it is possible that the RDAs for these eight nutrients are quite generous for most women. The food intake methods used in these studies may have underestimated true consumption. In the case of vitamin D, synthesis in the skin during summer months can contribute substantially to vitamin D adequacy. Finally, the number of women studied is relatively small, and women with medium to high incomes were underrepresented. These data should also be interpreted in light of the fact that even the well-balanced diets of healthy, nonpregnant adults provide low amounts of these same nutrients relative to the RDAs (King et al., 1978; Peterkin, 1986~. In the 1985 CSFII, a sample of all women aged 19 to 50 consumed less than three-quarters of their 1980 RDAs for iron, magnesium, calcium, zinc, vitamin Be, and folate (Peterkin, 1986~. (Vitamin D intakes were not reported.) Nonetheless, of these nutrients, the Report on Nutni;~on Moni- toring in the United States (LSRO, 1989) categorized only iron and calcium as food components that are recommended for high-priority monitoring status because they represent public health problems in the population. ASSOCIATIONS OF MATERNAL CHARACTERISTICS WITH NUTRIENT INTAKE DURING PREGNANCY Ethnic Background There have been no studies of both dietary and sociodemographic factors in a large, random sample of pregnant women in the United States. In a national sample of 1,503 women between the ages of 19 and 50, 93.4 % of whom were not pregnant or lactating (USDA, 1985), the most notable ethnic difference was calcium intake, which was 464 mg/day for blacks compared with 656 mg/day for whites (Peterkin, 1986~. The data in liable 13-2 suggest that this difference persists during pregnancy. In the National WIC Evaluation (Rush et al., 1988), in which all of the subjects were from low-income households, a few notable differences in intake were ascribed to ethnic background after a variety of maternal characteristics had been controlled statistically. Before registration in WIC, blacks had much lower intakes (703 mg/day) of calcium than did white non- Hispanics (1,045 mg/day), whereas Hispanic women consumed intermediate amounts (862 mg/day). Suitor et al. (1990) reported similar trends in calcium intake by ethnic groups among low-income pregnant women in Massachusetts. This situation may be explained in part by the much higher prevalence of lactose intolerance among blacks and Hispanics, sometimes resulting in their subsequent avoidance of milk. Data from one study (Villar et al., 1988) indicated that lactose intolerance abates during pregnancy, but this is unlikely to change dietary patterns substantially. Rush et al. (1988)

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268 DIETARY INTAKE AND NUTRIENT SUPPLEMENTS reported that enrollment in WIC was associated with 170- and 150-mg/day increases in calcium intake by blacks and Hispanics, respectively; however, average intakes remained low, especially for blacks. Lactose intolerance may not prevent blacks and Hispanics from consuming at least some of the dairy products supplied by WIC. It is also possible, however, that women reported a higher than actual consumption of the foods from the WIC package. Socioeconomic and Demographic Factors In the National WIC Evaluation (Rush et al., 1988), investigators ex- amined associations between nutrient intake and factors such as income and occupation at the time of registration in the program. In this analysis, the relationships between specific socioeconomic or demographic factors and intake were controlled for all other maternal characteristics at registration that might confound interpretation of the results by differentially affecting intake. These included maternal ethnic background, age, parity, history of low birth weight or infant death, cigarette smoking, alcohol intake, par- ticipation in assistance programs, income, family size, and parental work status. In these WIC-eligible, low-income women, employment was generally not associated with higher nutrient intakes and, in fact, was negatively related to calcium consumption. Wives of agricultural workers consumed substantially more energy, pro rein, and iron than did other women. The reasons for these associations were not established. On the other hand, Suitor et al. (1990) reported higher intakes of protein and zinc by employed rather than by unemployed low-income pregnant women. In the National WIC Evaluation, the number of people in the household had a minimal effect on nutrient intake by pregnant women. Income had a positive relationship to the intake of energy and protein by pregnant women: an additional 1.4 kcal of energy and 0.04 g of protein was consumed for every $100 per year increase in income. These results differ somewhat from those reported for the largely nonpregnant sample of women aged 19 to 50 who participated in CSFII. Their mean intakes of calcium; magnesium; iron; zinc; and vitamins Be, E, and folate increased slightly with income (Peterkin, 1986~. To some extent, the apparent effects of income in the CSFII analysis may be due to other demographic differences, such as household composition and lower proportions of blacks and Hispanics in the higher-income groups. WIC Participation The third-trimester mean intake of several nutrients by women who were WIC participants was significantly higher than that of nonparticipants

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DIETARY INTAKE 269 (Rush et al., 1988~. For protein, the intake was 5 g/day higher; for iron, 3.2 mg/day; for calcium, 133 mg/day; and for vitamin C, 32 mg/day. Vitamin A intake was unchanged. Among WIC participants there were also statistically significant higher daily intakes of energy (111 kcal), magnesium (25 mg), thiamin (0.34 lug), riboflavin (0.37 lug), niacin (3.2 mg), vitamin B6 (0.34 mg), and vitamin BE (1.3 Age. In a smaller study, Suitor et al. (1990) found that WIC participants had significantly higher intakes of protein, calcium, iron, and vitamin B6 per 1,000 kcal compared with nonparticipants. The strongest explanation for the higher intakes is the greater nutrient density of WIC foods compared with that of women's usual diets; the relative increases for most nutrients were higher than that for energy. In the National WIC Evaluation (Rush et al., 1988), the effects of WIC on nutrient intake appeared to be generally uniform across sociode- mographic groups, except for the greater improvements in calcium intake by blacks. The heaviest cigarette smokers also benefited more; WIC par- ticipation increased their intake of most nutrients. Maternal Age There are insufficient data from random national surveys to describe the effects of maternal age on nutrient intake during pregnancy, but data from CSFII and NHANES II indicate that intakes of most nutrients and of energy by women decrease with age (Carroll et al., 1983; USDA, 1985~. As shown in Table 13-2, there are wide differences among the reported intakes by pregnant teenagers in several small studies (Endres et al., 1985, 1987; Loris et al., 1985~. In contrast to the data on nonpregnant women, the National WIC Evaluation (Rush et al., 1988) indicated that younger women consumed less energy (intake increased by 18 kcal/day for each year of age), protein (0.5 g/year), and calcium (8 mg/year). SUMMARY Data on the reported dietary nutrient intakes by pregnant women stud- ied in the past decade show that the intakes of eight nutrients consistently average less than the 1989 RDAs, namely, vitamins Be, D, E, and folate; iron; calcium; zinc; and magnesium. Because of these apparent shortfalls, the subcommittee paid special attention to evidence regarding the need to supplement pregnant women with those nutrients. Somewhat less attention was directed toward protein; thiamin; riboflavin; niacin; and vitamins A, Bit, and C, because average dietary intakes generally meet the 1989 RDAs. The most notable relationship between ethnic background and dietary in- take is a lower consumption of calcium by blacks, Hispanics, and American Indians. WIC participation is associated with higher intakes of energy and a number of vitamins and minerals.

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270 DIETARY INTAKE AND NUTRIENT SUPPLEMENTS REFERENCES Beal, V.A. 1971. Nutritional studies during pregnancy. II. Dietary intake, maternal weight gain, and infant size. J. Am. Diet. Assoc. 58:321-326. Brandes, J.M. 1967. F~rst-trimester nausea and vomiting as related to outcome of pregnancy. Obstet. Gynecol. 30:427~31. Brennan, R.E., M.B. Kohrs, J.W. Nordstrom, J.P. Sauvage, and R.E. Shank. 1983a. Composition of diets of low-income pregnant women: comparison of analyzed with calculated values. J. Am. Diet. Assoc. 83:538-545. Brennan, R.E., M.B. Kohrs, J.W. Nordstrom, J.P. Sauvage, and R.E. Shank. 1983b. Nutrient intake of low-income pregnant women: laboratory analysis of foods consumed. J. Am. Diet. Assoc. 83:54~550. Butte, N.F., D.H. Calloway, and J.L. Van Duzen. 1981. Nutritional assessment of pregnant and lactating Navajo women. Am. J. Clin. Nutr. 34:2216-2Z8. Carroll, M.D., S. Abraham, and C.M. Dresser. 1983. Dietary Intake Source Data: United States, 1976-80. Vital and Health Statistics, Series 11, No. 231. DHHS Publ. No. (PHS) 83-1681. National Center for Health Statistics, Public Health Service, U.S. Department of Health and Human Services, Hyattsville, Md. 483 pp. Dwyer, J., and C.W. Suitor. 1984. Caveat emptor: assessing needs, evaluating computer options. J. Am. Diet. Assoc. 84:302-312. Endres, J.M., K. Poell-Odenwald, M. Sawicki, and P. Welch. 1985. Dietary assessment of pregnant adolescents participating in a supplemental-food program. J. Reprod. Med. 30:10-17. Endres, J., S. Dunning, S. Poon, P. Welch, and H. Duncan. 1987. Older pregnant women and adolescents: nutrition data after enrollment in WIC. J. Am. Diet. Assoc. 87:1011-1019. Hunt, I.F., N.J. Murphy, A.E. Cleaver, B. Faraji, M.E. Swendseid, AH. Coulson, V.A Clark, N. Laine, C.A. Davis, and J.C. Smith, Jr. 1983. Zinc supplementation during pregnancy: zinc concentration of serum and hair from low-income women of Mexican descent. Am. J. Clin. Nutr. 37:572-582. IOM (Institute of Medicine). 1988. Prenatal Care: Reaching Mothers, Reaching Infants. Report of the Committee to Study Outreach for Prenatal Care, Division of Health Promotion and Disease Prevention. National Academy Press, Washington, D.C. 254 PP. King, J. C., S.H. Cohenour, C.G. Corruccini, and P. Schneeman. 1978. Evaluation and modification of the basic four food guide. J. Nutr. Educ. 10:27-29. Klebanoff, M.A., P.A. Koslowe, R. Kaslow, and G.G. Rhoads. 1985. Epidemiology of vomiting in early pregnancy. Obstet. Gynecol. 66:612-616. Loris, P., KG. Dewey, and K. Poirier-Brode. 1985. Weight gain and dieta~y intake of pregnant teenagers. J. Am. Diet. Assoc. 85:1296-1305. LSRO (Life Sciences Research Office). 1989. Nutrition Monitoring in the United States: An Update Report on Nutrition Monitoring. Prepared for the U.S. Department of Agriculture and the U.S. Department of Health and Human Services. DHHS Publ. No. (PHS) 89-1225. U.S. Government Printing Office, Washington, D.C. (various pagings). NRC (National Research Council). 1982. Alternative DietaIy Practices and Nutritional Abuses in Pregnancy: Proceedings of a Workshop. Report of the Committee on Nutrition of the Mother and Preschool Child, Food and Nutrition Board, Commission on Life Sciences. National Academy Press, Washington, D.C. 211 pp. NRC (National Research Council). 1989. Recommended Dieta~y Allowances, 10th ed. Report of the Subcommittee on the Tenth Edition of the RDAs, Food and Nutrition Board, Commission on Life Sciences. National Academy Press, Washington, D.C. 284 PP. Olson, J.A. 1987. Recommended dietary intakes (RDI) of vitamin A in humans. Am. J. Clin. Nutr. 45:704-716. Peterkin, B.B. 1986. Women's diets: 1977 and 1985. J. Nutr. Educ. 18:251-257.

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DIETARY INTAKE 271 Picone, T.A., L~H. Allen, M.M. Schramm, and P.N. Olsen. 1982. Pregnancy outcome in North American women. I. Effects of diet, cigarette smoking, and psychological stress on maternal weight gain. Am. J. Clin. Nutr. 36:1205-1213. Rush, D., N.L. Sloan, J. Leighton, J.M. Alvir, D.G. Horowitz, W.B. Seaver, G.C. Garbowski, S.S. Johnson, R.A. Kulka, M. Holt, J.W. Devore, J.T. Lynch, M.B. Woodside, and D.S. Shanklin. 1988. The National WIC Evaluation: Evaluation of the Special Supplemental Food Program for Women, Infants, and Children. V. Longitudinal study of pregnant women. Am. J. Clin. Nutr. 48:439-483. Suitor, CJ.W., J. Gardner, and W.C. Millets. 1989. A comparison of food frequency and diet recall methods in studies of nutrient intake of low-income pregnant women. J. Am. Diet. Assoc. 89:1786-1794. Suitor, C.W., J.D. Gardner, and MALE Feldstein. 1990. Characteristics of diet among a culturally diverse group of low-income pregnant women. J. Am. Diet. Assoc. 90:543-549. Taggart, N. 1961. Food habits in pregnancy. Proc. Nutr. Soc. 20:35-40. Taper, LO., J.T. Oliva, and S.J. Ritchey. 1985. Zinc and copper retention during pregnancy: the adequacy of prenatal diets with and without dietary supplementation. Am. J. Clin. Nutr. 41:1184-1192. Tierson, F.D., CALF Olsen, and E.B. Hook. 1985. Influence of cravings and aversions on diet in pregnancy. Ecol. Food Nutr. 17:117-129. Tierson, F.D., C.L. Olsen, and E.B. Hook. 1986. Nausea and vomiting of pregnancy and association with pregnancy outcome. Am. J. Obstet. Gynecol. 155:1017-1022. USDA (I:J.S. Department of Agriculture). 1985. Nationwide Food Consumption Survey. Continuing Survey of Food Intakes by Individuals. Women 19-50 Years and Their Children 1-5 Years, 1 Day, 1985. Report No. 85-1. Nutrition Monitoring Division, Human Nutrition Information Service, U.S. Department of Agriculture, Hyattsville, Md. 102 pp. Villar, J., E. Kestler, P. Castillo, A. Juarez, R. Menendez, and N.W. Solomons. 1988. Improved lactose digestion during pregnancy: a case of physiologic adaptation? Obstet. Gynecol. 71:697-700. Worthington-Roberts, B., R.E. Little, M.D. Lambert, and R. Wu. 1989. Dietary cravings and aversions in the postpartum period. J. Am. Diet. Assoc. 89:647-651.