J Clin Epidemiol Vol. 44, No. 4/5, pp. 423428, Printed in GreatBritain.All rightsreserved

0895-4356/91$3.00+ 0.00 Copyright 0 1991Pergamon Press plc

1991

MATERNAL WEIGHT GAIN, DIET AND INFANT BIRTH WEIGHT: CORRELATIONS DURING ADOLESCENT PREGNANCY THERESA 0.

SCHOLL,* MARY L. HEDIGER, CHOR-SAN KHOO,

MARY FRANCES HEALEY

and

NANCY L. RAWSON

Departments of Obstetrics and Gynecology, University of Medicine and Dentistry of New Jersey-SOM and RWJMS, Cooper Hospital/University Medical Center and Campbell Institute of Research and Technology, Camden, NJ 08103, U.S.A. (Received in revired form 17 July 1990)

Abstract-Inadequate weight gain during pregnancy is an important risk factor for low birth weight (LBW), but the contribution of diet to weight gain is uncertain. Pregnancy weight gains were examined at 4-week intervals from 12 to 36 weeks’ gestation, as well as total gain for gestation, in a cohort of over 2000 young pregnant women, aged < 18 at entry to prenatal care. The effect of diet was studied in a 15% random sample of the cohort, using a 24-hour dietary recall obtained at entry to prenatal care (averaging 17 weeks’ gestation). As early as 16 weeks’ gestation, gains below the lower limit of a clinical standard were associated with a decrement in birth weight at delivery of more than -85 g (p < O.Ol), and after 24 weeks of approximately - 180 g (p < 0.001). After adjusting for potential confounding variables, teenagers who went on to develop inadequate total weight gain for gestation had consumed 1878 kcal vs 2232 for teenagers with adequate total gain (p < 0.05). There were significant deficits in protein (p < 0.05) and carbohydrate intake (p < 0.05) associated with inadequate gain. However, there was no direct effect of nutrient intake on birth weight, LBW, or preterm delivery. This suggests that the relationship between nutrient intake during pregnancy and birth weight may be indirect and moderated by weight gain during pregnancy. Low birth weight

Weight gain

Adolescent pregnancy

INTRODUCTION

Dietary intakes

ante for the pregnant teenager. Even when gains are adequate over the whole of adolescent pregnancy, inadequate gains before 24 weeks’ gestation arc associated with decreased birth weight and a 2-fold increase in the risk of LBW [5]. Consistent with this are observations on Baltimore teenagers where increased risk of infant LBW was associated with a decrement in arm fat area measured between 22 and 32 completed weeks, as opposed the positive increment observed among same-age controls who did not deliver a LBW infant [8]. These findings also imply that, under certain conditions, maternal nutritional status and intake have a important influence on pregnancy

Many studies [l-3] have demonstrated that maternal weight gain during pregnancy and the weight of the infant at delivery are positively correlated. Low gestational gain is known to be one of the strongest predictors of low birth weight (LBW), including both preterm [4-71 and small-for-gestational-age births [5-71. While this may be true for adult gravidas in general, weight gain may have even greater prognostic import*All correspondence should be addressed to: Dr Theresa 0. Scholl, Department of Obstetrics and Gynecology, UMDNJ-SOM, 401 Haddon Avenue, Camden, NJ 08103-1505, U.S.A. [Tel: (609) 757-77351. 423

424

THERESA

0.

course and outcome. Maternal diet, a presumed correlate of the weight that is gained during pregnancy, may be an important underlying cause of the increased risk of LBW and other poor outcomes associated with adolescent pregnancy. Despite this, there has been no demonstration in the adolescent [9, lo] that maternal intake affects either gestational weight gain or pregnancy outcome. Only a limited literature [ 1l-201 is available documenting such effects in mature women. With these in mind, we examined cumulative weight gain as well as dietary intakes obtained during the course of adolescent pregnancy, using data from a geographically based cohort of young pregnant women to answer three major questions: (1) how early in pregnancy is the association of inadequate weight gain and reduced birth weight detectable, (2) do adolescents with inadequate weight gain have reduced dietary intakes, and (3) is there a direct relationship between maternal dietary intakes and birth weight?

MATERIALS AND METHODS

A total of 2789 adolescents were registered into the Camden County Adolescent Family Life Program, a federally-funded demonstration which provided comprehensive prenatal care, including counseling about diet and weight gain during pregnancy, to low-income pregnant teenagers. Methods of the study have been described [5-71. Maternal weight was measured with a beam balance scale at each prenatal visit over the course of pregnancy, and a cumulative gain was computed by subtracting recalled prepregnant weight from measured weight at 4-week intervals from 12 completed weeks’ gestation. There is excellent agreement between stated and measured weight in mature women [22-231 and between weight measured before pregnancy and stated prepregnancy weight (Y = 0.98) in adolescents [24]. Linear interpolation was used for measurements taken more than a week beyond the 4-week interval. A published schedule of weight gain for gestation was then used to adjust for pregnancy duration and to define inadequate weight gain below the lower limit of the “standard curve” at each gestational age [25,26]. A total was also computed by cross-classifying weight gain at delivery, or the last prenatal visit, with gestation to define total inadequate gain for the whole of pregnancy. This was done in order to control for

SCHOLL

et al.

Table 1. Cutpoints* for inadequate weight gain for gestation Gestation (wk)

Gain (kg)

12 16 20 24 28

0.7 1.6 2.8 4.3 5.8

Gestation (wk) 32 36 31 38 39+

Gain (kg) 7.4 9.0 9.2 9.1 9.9

*Cutpoints are derived from weight gain charts published by Butman [25] and Rosso [26].

confounding between the length of gestation and the amount of weight gained during pregnancy. For example, at 39 completed weeks’ gestation an indequate total corresponded to a weight gain of less than 9.9 kg (Table 1). Of the 2789 registrants, 288 failed to return to the clinic before delivery, 101 were excluded with a pregnancy loss, 20 with liveborn multiple births, and 9 with Asian ancestry, leaving a base sample of 2371 adolescent gravidas. In addition, 363 who lacked data on weight gain during pregnancy were excluded, leaving a total of 2008 young women with liveborn, singleton deliveries as well as data on weight gain during pregnancy. Patients with and without data on weight gain were similar in age, prepregnant Body Mass Index (BMI) and infant birth weight. They differed (p < 0.05) in length of gestation (those with weight gain data had gestations 0.6 week longer), parity (79.1% of those with data were primiparas vs 64.5%), and ethnicity (36.8% of those with data were white vs 24.9%). At entry to prenatal care, dietary data were obtained by registered dietitians, experienced with the method, on a 15% random sample of the 2371 cohort members. A 24-hour recall of the previous day’s diet was elicited, and 3-dimensional food models were used to quantify portion size. Information about concurrent nausea and vomiting of pregnancy was collected at the time of the recall. It is well recognized that a single 24-hour recall will reliably characterize nutrient intake of a group, but not of an individual [27]. Nutrient intakes of macro-nutrients (calories, protein, carbohydrate, fat) and micro-nutrients (iron, folacin, zinc, sodium, calcium, beta-carotene, and vitamin A) were calculated using the Cambell Master Nutrient Data Base, which utilizes the Michigan State University Nutrient Data Base, the USDA Nutrient Data Base, as well as other sources. Multiple linear regression and analysis of covariance 1281 were used to examine weight

Weight Gain and Diet in Adolescent Pregnancy

gain and nutrient intakes. Multiple linear regression was used hierarchically, by entering variables in a predetermined order to partial out effects of confounding variables prior to consideration of weight gain or diet on birth weight and the effects of diet on weight gain. All variables in Table 2 were examined as potentially confounding variables. Inspection of residuals from regression for departures from linearity [29] showed a normal distribution for every model. RESULTS

Background characteristics of the cohort and the 15% random sample providing dietary data are shown, Table 2. Approximately 16% were between the ages of 12 and 15 years, 77% were either black or Hispanic, and nearly 80% had Medicaid as the sole source of financing for prenatal care and delivery costs. Nearly 25% smoked or had a low BMI, and 22% had an inadequate total weight gain for gestation. A comparison of the random sample to the cohort (Table 2) showed no significant differences and little absolute divergence in characteristics which are known to influence pregnancy outcome. Differences in the infant weight at delivery associated with inadequate pregnancy weight Table 2. Background characteristics* of random sample compared to CCAFL (Camden County Adolescent Family Life Project) cohort CCAFL cohort

Random sample

Age (Y~I 12-15 16-17 18-19

325 886 787

16.2% 44.1% 39.1%

59 166 130

16.6% 46.8% 36.6%

Ethnicity Hispanic Black White

461 807 738

23.0% 40.2% 36.8%

90 163 102

25.4% 45.9% 28.7%

543 1100

27.4% 55.6%

89 204

25.1% 57.5%

336

17.0%

62

17.5%

32.1% 54.9% 12.4%

129 176 50

36.3% 49.6% 14.1%

1585 1507 647

79.1% 76.5% 32.5%

290 215 93

81.9% 79.3% 26.2%

437

20.9%

17

21.7%

Prepregnan t BMI Low BMI (< 19.5) Normal BMI High BMI (>24.5)

Trimester at Enlry to Care First 645 Second 1084 Third 244 Primigravid Medicaid Smoking Weight gain inadequate

*Sample sizes vary slightly because of missing data.

425

Table 3. Decrement in infant weight at birth (g) attributable to inadequate weight gain Weeks’ gestation

Sample size

Estimated coefficient

SE

12 16 20 24 28 32 36

619 1010 1338 1582 1799 1880 1777

- 10.83 g -85.77** - 143.40** - 183.38** - 175.39** - 174.25** - 186.91**

39.98 31.80 29.18 29.22 27.64 27.83 28.30

Regressions of inadequate maternal weight gain for gestation on birth weight were fitted at each gestational age after controlling for gestation at delivery, ethnicity, maternal prepregnant body mass index, smoking, age and parity. Sample sizes vary with gestation at entry to care, compliance with prenatal care schedules, and gestation at delivery. **Estimate significant at p < 0.001.

gain defined earlier in gestation are shown by gestational age for the cohort as a whole in Table 3. As early as 16 weeks’ gestation, there was a significant deficit (- 85.8 f 31.8 g, p < 0.001) in infant weight at delivery between those with an inadequate gain and those whose gain was judged to be adequate at week 16. By mid-pregnancy (20 weeks), the birth weight difference between those with adequate and indequate gain for gestation amounted to - 143.4 (k29.2) g. At 24 weeks the deficit in weight at birth was increased to about - 180 g and remained at this level, for those with inadequate gain, until term. There was also a substantial birth weight deficit for patients with inadequate total pregnancy weight gain, estimated by cross-classifying the total gain with gestation at delivery. For the cohort as a whole, the birth weight difference amounted to - 191.4 f 27.4 g (p > 0.001). For the 15% random sample the deficit was - 181.4 f 70.4 g (p < 0.01). There was a statistically significant difference in dietary intakes at entry to prenatal care for young women who went on to have an inadequate total gain for gestation (Table 4). After control for confounding, there were significant deficits in kilocalories (- 353 kcal), protein (- 16.8 g), and carbohydrates (-41.5 g) as well as total grams of food ingested (- 338 g). Nausea and vomiting slightly decreased caloric intake by about 100 g, but this effect was not statistically significant (p > 0.40). Decreased intake or macro-nutrients was associated mainly with reduced caloric intakes (Table 5). After including calories in the model, there was little difference in protein, carbohydrate and total grams ingested, suggesting

THERESA 0. SCHOLLet al.

426

Table 4. Caloric and macro-nutrient intakes (24-hour recall) at entry to prenatal care for CCAFL teenagers with adequate and inadequate weight gain for gestation Inadequate (n = 77)

Table 6. The relationship between caloric intake and pregnancy outcomes Caloric intake

Adequate (n = 278)

Intake

Mean

SEM

Mean

SEM

Kilocalories Protein (g) Fat (g) Carbohydrates Sugar (g) Total grams

1878.5 74.7 79.7 221.4 113.6 1773.9

149.0 6.3 8.2 17.6 9.8 164.9

223 1.9* 91.5* 91.5 262.9’ 119.9 2111.7

68.6 2.9 3.8 8.1 4.5 76.0

Intakes are controlled for ethnic group, smoking, and prepregnant BMI. *Significant at p < 0.05.

that the differences initially observed could be explained in large part by lower overall intake in those with indequate gain. However, there was a tendency (p < 0.10) for gravidas with inadequate gain to have lower iron intakes (Table 5), suggesting that qualitative dietary differences in micro-nutrient intake might play a role as well. Finajly, there was little direct effect of maternal diet on pregnancy outcome (Table 6), when outcome was measured as LBW, preterm delivery, or small-for-gestational-age [29]. Consistent with these findings, the direct relationship of calories to birth weight was weak (0.035 g increase in birth weight/calorie) and not statistically significant. DISCUSSION

We examined the relationship between dietary intake at entry to prenatal care, weight gain for gestation, and infant birth weight in a geographical cohort of pregnant teenagers. Weight gain was scored as adequate or in-

Birth weight < 2500 g 3 2500 g Small-for-gestational-age Appropriate-for-gestation Preterm (< 37 weeks) Term delivery (2 37 weeks)

n

Mean

SEM

41 303 25 316 39 310

2203.2 2185.0 2028.1 2201.2 2163.5 2180.7

173.5 64.1 221.7 62.6 179.4 63.1

Intakes are controlled for ethnicity, adequacy of weight gain, smoking, and prepregnant BMI. Sample sizes may vary because of missing data.

adequate for gestation using a clinical schedule [25,26], which controlled for confounding between duration of gestation and amount of weight gained during pregnancy. Using this approach, we detected a significant association between calories ingested at entry to care and inadequate total weight gain, and between maternal gain and weight of the infant at birth. There was no direct association between caloric intake and pregnancy outcome. Although weight gain during pregnancy is known to be associated strongly with both infant birth weight and length of gestation [l-7], only a few prior studies have examined risks associated with abnormally low weight gains during the first and second trimesters. In the current study, we detected a significant relationship between inadequate weight gain for gestation and birth weight which amounted to -85 g for those with inadequate gains early in the second trimester (16 weeks’ gestation) and increased to - 180g or more for those with inadequate gain after mid-pregnancy. Thus, the effects of inadequate weight gain were detectable early and throughout pregnancy starting in

Table 5. Calorie-adjusted macro- and micro-%rient intakes for CCAFL teenagers with adequate and inadequate w+ight gain for gestation Inadequate (n = 77)

Adequate (n = 278)

Intake

Mean

SEM

Mean

SEM

Protein (g) Fat (g) Carbohydrates Sugar (g) Total grams Vitamin A (IU) Beta-carotene Folacin (pg) Iron (mg) Calcium (mg) Sodium (mg) Zinc (ma)

85.6 94.7 252.3 125.6 1965.1 5833.7 1585.2 269.5 17.2 1077.9 3589.0 12.1

3.4 3.5 8.7 7.8 135.8 1309.2 487.0 47.3 2.9 72.6 230.0 1.1

89.6 89.3 257.4 117.8 2077.8 6511.4 2000.2 345.7 22.7 1077.0 3543.4 13.3

1.5 1.6 4.0 3.6 62.3 600.2 223.3 21.7 1.3 33.3 105.5 0.5

Intakes are controlled for calories, ethnicity, smoking, and prepregnant BMI.

Weight

Gain and Diet in Adolescent

the second trimester. Other studies using data from the cohort as a whole [6,7,30] have shown that an inadequate total weight gain triples the risk of LBW and small-for-gestational-age births and approximately doubles the risk of preterm delivery [6]. In addition, excessive weight gain (at the 75th percentile for the cohort) more than doubled the risk of fetal macrosomia ( > 4000 g) [30]. Thus, maternal weight gain at either end of the spectrum influences infant birth weight. In this study inadequate total gain was associated with decreased energy intake early in pregnancy. Examination of the relationship between dietary intake and weight gain for gestation in a random sample of the cohort revealed that the intakes of calories and other macro-nutrients were lower among those with inadequate total weight gain. The difference between those with adequate and inadequate gain amounted to approximately 350 kcal, approximately equivalent to the recommended daily caloric increase for pregnancy [31]. We were unable to attribute differences in caloric intake to nausea and vomiting of pregnancy. Because intakes were obtained at entry to care and because nausea and vomiting of pregnancy is primarily confined to the first trimester, we may have missed an effect of nausea and vomiting on early intake because of the timing of entry to care. However, as far as we are aware a demonstration of a link between early weight gain, caloric intake, and nausea and vomiting has not been securely made, and remains a possibility in the etiology of inadequate early weight gain. After adjustment for calories, there was little difference in macro-nutrients ingested by young women with adequate or inadequate gains, suggesting that differences in adequacy of maternal gain were driven primarily by dietary differences in energy. That is, the absolute quantity of intake was lower, while the quantity and balance among nutrients did not reveal any specific deficiency, e.g. of protein. After adjustment for calories, there was some indication that micro-nutrients in the diet during pregnancy might be lower for teenagers with total inadequate gain. There was a tendency for young women with inadequate gain to have diets lower in iron. A diet chronically low in iron could affect expansion of the red cell mass, in turn affecting expansion of maternal plasma volume, one of the components of weight gain during pregnancy.

Pregnancy

427

The relationship between diet and weight gain during pregnancy, when detected, has not been particularly strong. For example, in 1959 Thomson reported a correlation of 0.30 between caloric intake and weight gain in Aberdeen primigravidas whose dietary intakes were unrestricted [ 151.Since then, the attenuated magnitude of this association has been confirmed in observational studies in the U.S. and Canada, although the relationship (maternal weight and caloric rations) was also present in the Dutch Famine study [14] and the supplementation trial carried out in Harlem by Rush et al. [16]. In part, this may be a function of maternal body composition during pregnancy. Apart from the weight of the fetus, gestational gain is mostly water, as opposed to maternal tissue. One would not anticipate a particularly close relationship between extracellular and/ or extravascular fluid accumulation and the caloric content of the maternal diet [15]. The association between maternal fat accumulation during pregnancy and dietary intake has never been examined, as far as we are aware. Our finding a lack of a direct effect of diet on pregnancy outcome is congruent with the reports of other investigators [12, 15, 16, 18, 191. However, the nature of the relationship between diet and weight gain [12-l 91 and between weight gain and birth weight [13-16, 18, 191 in these studies suggests that fetal growth may rely on energy stored, as opposed to calories just ingested. The well-recognized relationship between infant weight at birth and maternal prepregnant weight [I], an indicator of the nutrient stores available for pregnancy, is consistent with this hypothesis. There is a notable exception. When maternal stores are low or depleted, as in the case of famine [14] or under conditions of frankly intractable poverty [17], there may be a more direct relationship between maternal intake and birth weight. However, a reliance on deposited, as opposed to ingested calories, would ordinarily be protective in case of periodic scarcity or a more acute problem, such as nausea and vomiting persisting after the first trimester of pregnancy [32,33]. The implications of these findings for clinical care are that preconceptional nutritional status of high risk adolescents may require monitoring and intervention. Further, modification of early weight gain by improving the quantity, and possibly the quality, of the maternal diet may alter the birth weight

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distribution of U.S. infants to one favoring lower levels of infant mortality.

14. Stein Z, Susser M. The Dutch Famine, 194&1945, and

Acknowledgements-This study was supported by Grant HD18269 from The National Institute of Child Health and Human Development and APHO00522 from the Office of Population Affairs, Department of Health and Human Services.

15. Thomson AM. Diet in pregnancy. 3. Diet in relation to the course and outcome of pregnancy. Br J Nutr 1959; 13: 509-524. 16. Rush D, Stein Z, Susser M. Diet in pregnancy: a randomized controlled trial of nutritional supplements. Birth Defects: Original Article Series. 1980: Vol. XVI, No. 3. 17. Lechtig A, Habicht J-P, Klein ‘R, Yarborough C, Martorell R. Effect of food supplementation during pregnancy on birthweight. Pediatrics 1975; 56:

the reproductive process. II. Interrelations of caloric rations and six indices at birth. Pediat Res 1975; 9: 7683.

REFERENCES

508-520.

1. Committee to Study the Prevention of Low Birthweight. Preventing Low Birthweight. Washington, D.C.: National Academy Press; 1985. 2. National Center for Health Statistics, Taffel SM. Matemal

3. 4.

5.

6.

7.

8.

9.

10.

11.

12.

13.

Weight

Gain and the Outcome

of Pregnancy,

Vital and Health Statistics. Series 21. No. 44. DHHS Publication No. PHS (s6-1922). Hyattsviile, Md: National Center for Health Statistics; 1986. Naeye RL. Weight gain and the outcome of pregnancy. Am J O&et Gynecol 1979; 135: 3-9. Abrams B, Neuman V, Key T, Parker J. Maternal weight gain and preterm delivery. Obstet Gynecol 1989; 74: 577-583. Hediger ML, Scholl TO, Belsky DH, Antes IG, Salmon RW. Patterns of weight gain in adolescent pregnancy: effects on birth weight and preterm delivery. Obstet Gynecol 1989; 74: 612. Scholl TO, Hediger ML, Salmon RW, Belsky DH, Antes IG. The influence of prepregnant body mass and weight gain for gestation on spontaneous preterm birth and duration of gestation during adolescent pregnancy. Am J Hum Biol 1989; 1: 657464. Hediger ML, Scholl TO, Salmon RW. Early weight gain in adolescent pregnancy and fetal outcome. Am J Hum Biol 1989; 1: 6655672. Maso MJ, Gong EJ, Jacobson MS, Bross DS, Heald FP. Anthropometric predictors of low birth weight outcome in teenage pregnancy. J Adolesc Health Care 1988; 9: 188-193. King JC, Cohenour SH, Galloway DH, Jacobson HN. Assessment of nutritional status of teenage pregnant girls. 1. Nutrient intake and pregnancy. Am J Clin Nutr 1972; 25: 916-925. Ancri G, Morse E, Clarke RP. Comparison of the nutritional status of pregnant adolescents with adult pregnant women. III. Maternal protein and calorie intake and weight gain in relation to infant size at birth. Am J Clin Nutr 1977; 30: 568-572. Doyle W, Crawford MA, Laurance BM. Dietary survey during pregnancy in a low socio-economic group. Proc Nutr Sot 1982; 41: 44A. Haworth JC, Ellestad-Sayad JJ, King J, Dilling L. Fetal growth retardation in cigarette-smoking mothers is not due to decreased maternal food intake. Am J Obstet Gynecol 1980; 137: 719-723. Picone TA, Allen LH, Olsen P, Ferris M. Pregnancy outcome in North American women. II. Effects of diet, cigarette smoking, stress and weight gain on placentas and on neonatal physical and behavioural characteristics. Am J Clin Nutr 1982; 36: 1214-1224.

18. Aaronson LS, Macnee CL. The relationship between weight gain and nutrition in pregnancy. Nursing Res 1989; 38: 223-227.

19. Beal VA. Nutritional studies during pregnancy. II. Dietary intake, maternal weight gain and size of infant. J Am Diet Assoc 1971: 58: 321-326.

Osofsky HJ. Relationships between prenatal medical and nutritional measures, pregnancy outcome, and early infant development in an urban poverty setting. Am J Obstet Gynecol 1975; 123: 682-690. 21. Durnin JVGA, McKillow FM, Grant S, Fitzgerald G. Energy requirements of pregnancy in Scotland. Lancet

20.

1987; i: 897-900. Stewart AL. The

reliability and validity of selfreported weight and height. J Chron Dis 1982; 35: 295-309. 23. Palta M, Prineas RJ, Berman R, Hannon P. Comparison of self-reported and measured height and weight. Am J Epidemiol 1982; 115: 223-230. 24. Stevens-Simon C, McAnarney ER, Coulter MP. How accurately do pregnant adolescents estimate their weight prior to pregnancy? J Adolesc Health Care 1986; 7: 250-254. 2s. Butman M. Prenatal Nutrition: a Clinical Manual. 22.

26. 27. 28.

Massachusetts Department of Health; 1982. Rosso P. A new chart to monitor weight gain during pregnancy. Am J CIln Nutr 1985; 41: 644-652.

Block G. A review of validation of dietary assessment methods. Am J Epidemiol 1982; 115: 492-505. Kleinbaum DG, Kupper LL, Muller KE. Applied Regression Analysis and Other Multivariable 2nd edn. Boston: PWS-Kent; 1988.

29.

30.

31.

32.

33.

Methods,

Brenner WE, Edelman DA, Hendricks CH. A standard of fetal growth for the United States of America. Am J Obstet-Gynecol 1976; 126; 555-564. Scholl TO. Hedieer ML. Antes IG. Belskv DH. Salmon RW. Weig& gain during pregnancy in >doles: cence: predictive ability of early weight gain. Obstet Gynecol 1990; 75: 948-953. Food and Nutrition Board. Recommended Dietary Allowances, 9th edn. Washington, D.C.: National Academy of Sciences; 1980. Tierson FD, Olsen CL, Hook EB. Nausea and vomiting of pregnancy and association with pregnancy outcome. Am J Obstet Gynecol 1986; 155: 1017-1022; 1989; 160: 518-519. Behrman CA. Hedieer ML. Scholl TO. Arkanael CM. Nausea and vbmitini during teenage pregnancy: effects on birth weight. J Adolesc Health Care 1990; 11:

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Maternal weight gain, diet and infant birth weight: correlations during adolescent pregnancy.

Inadequate weight gain during pregnancy is an important risk factor for low birth weight (LBW), but the contribution of diet to weight gain is uncerta...
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