Determinants of Gestational Weight Gain
Determinants of gestational weight gain include a range of biological, metabolic, and social factors. Several workshop speakers discussed the base of knowledge and current understanding of the complicated relationship between biological and social factors in determining gestational weight gain. In addition, they indicated how this research could provide insight on factors that may impede or foster compliance with the recommended guidelines for gestation weight gain. This chapter is framed by speakers at the workshop; distinguishing between biological factors and social factors poses a significant challenge as knowledge is gained about the nature of their interactions. Many processes involve both components.
GESTATIONAL WEIGHT GAIN
Janet King observed that gestational weight gain includes three components: (1) the products of conception (i.e., the fetus, placenta, and amniotic fluid), (2) maternal tissues (i.e., uterus, mammary, and blood), and (3) maternal fat reserves. The fat reserves comprise about 30 percent of the total gain on average. The components of gain can also be divided into water, about 65 percent of the total, fat, about 30 percent and the most variable, and protein, the remaining 5 percent (Butte et al., 2003; Hytten and Chamberlain, 1980; Kopp-Hoolihan et al., 1999).
Recommended Gestational Weight Gain
The 1990 Institute of Medicine (IOM) report Nutrition During Pregnancy recommended guidelines for gestational weight gain. To derive the
recommendations, gestational weight gain was summarized for women in different prepregnancy body mass index (BMI) groups giving birth to infants weighing between 6.6 and 8.8 lbs., which was considered the normal range of infant birth weight with good outcomes. The range of reported gestational weight gain, which was extremely wide, was then narrowed by the committee to the resultant IOM recommendations (Table 2-2). Abrams and Parker (1990) reported the mean gestational weight gains of women with good outcomes (i.e., infants with birth weights within the normal range) in very similar BMI groups to those used by the IOM committee. The gestational weight gains of women in the underweight and normal-weight groups were generally consistent with the IOM recommendations, but the gains of overweight and obese women exceeded the recommendations. Wells et al. (2006) reported the odds ratio of gaining either above or below the IOM’s recommended range was high in women with a prepregnancy BMI greater than 29 compared with women with prepregnancy BMI of 19.8 to 26—an odds ratio of 19 of gaining above and nearly 7 of gaining below.
Recommended Rate of Gestational Weight Gain
The 1990 IOM committee also recommended a rate of weight gain during pregnancy to facilitate the clinical monitoring of weight changes in pregnant women (Institute of Medicine, 1990). The recommendations were based on data from the 1980 National Natality Survey. For normal-weight women, a gain of about 0.9 lb/week in the second and third trimesters was suggested; overweight or obese women were advised to gain slightly less and underweight women slightly more. Studies of rates of gestational weight gain show that women deviate considerably from these recommendations. Data from over 113,000 women in the Pregnancy Risk Assessment Monitoring System (PRAMS) showed that very low rates of gain (<0.26 lb/week) were more prevalent for obese and very obese women, 8 and 19 percent, respectively, than in underweight and normal-weight women, 2 percent in both groups (Dietz et al., 2006). About 10 percent of the women gained weight at twice the recommended weight (more than >1.7 lbs/week).
Pattern of Gestational Weight Gain
Studies of the pattern of gestational weight gain help to determine when the greatest rate of gain occurs and how it varies with maternal prepregnancy BMI. Both Butte et al. (2003) and Carmichael et al. (1997) reported greater rates of weight gain in the second trimester compared with the third, with lower average rates in overweight or obese women. However, the pattern of gain differed in a study of 1,367 Filipino women who
started pregnancy weighing less than the typical American woman (Siega-Riz and Adair, 1993). Underweight women (BMI <18.5) gained more weight during pregnancy than normal-weight or overweight women due to higher gains in the first trimester. Overweight women (BMI >25) lost a small amount of weight in the first trimester, but they gained at a more rapid rate in the third trimester, when fetal growth rates are the highest. In sum, King observed, studies suggest that the rate of maternal weight gain during the first half of pregnancy, when fat stores are accumulating, tends to be lower in women with higher amounts of fat stores at conception. Also, the average rate of weight gain during pregnancy among U.S. women is greater than the 0.9 lb./week recommended by the 1990 IOM report.
BIOLOGICAL AND METABOLIC FACTORS OF GESTATIONAL WEIGHT GAIN
King provided an overview of the role of biological and metabolic factors in gestational weight gain. Studies of the influence of biological and metabolic factors tend to be cross-sectional and observational, with relatively small sample sizes. Although it is difficult to draw any conclusions about the link between these factors and gestational weight gain, two themes emerge from the research conducted to date: (1) interactions among several biological factors (i.e., prepregnancy weight, age, parity, and stature) influence gestational weight gain and (2) the biological influences on gestational weight gain vary widely among women. Other potential metabolic factors that may affect gestational weight gain (i.e., placental secretions or metabolic changes in obese women) remain poorly understood.
Prepregnancy Body Mass Index
In 1990, the IOM committee concluded that maternal prepregnancy BMI is a primary determinant of gestational weight gain and referenced all of its recommendations to prepregnancy BMI (Institute of Medicine, 1990). Research studies presented at the workshop continue to support this conclusion.
The effect of maternal age on gestational weight gain has been studied almost exclusively in young (adolescent) mothers; no data from older mothers were located. Three new studies of gestational weight gain in adolescents have been published since the IOM report was released in 1990 (Hediger et al., 1990; Johnston et al., 1991; Stevens-Simon et al., 1993). As reported in the 1990 IOM report, these studies suggest that the ratio of
infant birth weight to maternal gestational weight gain tends to be lower among adolescents than adults, and higher gestational weight gains do not improve birth weight in infants born to adolescent mothers. One study has reported higher rates of total gestational weight gain among adolescent mothers than among adults (Hediger et al., 1990).
The 1990 IOM report reported that multiparous women tend to gain less weight than primiparous women (i.e., first-time mothers). A comprehensive study of 523 women in the United Kingdom confirmed this finding (Harris et al., 1997). In addition, two studies found that high parity is associated with a higher BMI later in life due to weight retention following each pregnancy (Harris et al., 1997; Wolfe et al., 1997). As mentioned in the previous section, higher prepregnancy BMI is the primary determinant of gestational weight gain. King described one study of U.S. women that found ethnic variations in the relationship between parity and body weight (Wolfe et al., 1997). In this study, black women who were underweight at conception tend to retain about twice as much weight following a pregnancy than do underweight white women. Elizabeth McAnarney noted that young primiparous adolescents are at particular risk for greater weight gain (Howie et al., 2003).
Data on the effect of maternal height on gestational weight gain are very limited. In 1990, the IOM committee reported that short women (<62 in) tend to gain less than taller (>67 in) women (Institute of Medicine, 1990). In a study of 4,791 Hispanic women living in Los Angeles, short stature (<62 in) increased the risk of poor total weight gain by 50 percent among underweight and normal-weight women, but not among overweight or obese women (Siega-Riz and Hobel, 1997). The interactions among maternal prepregnancy BMI status and stature in affecting gestational weight gain need further evaluation.
Determinants of Maternal Fat Gain
Fat gain is the most variable of the three components (water, fat, and protein) of maternal weight gain. The amount of fat gained is more strongly associated with total weight gain than any other component (Butte et al., 2003; Kopp-Hoolihan et al., 1999). It also is the component of gestational weight gain that contributes to higher BMI later in life. For example, in a small study of 10 women who were similar in terms of race/ethnicity,
weight status at conception, and parity, maternal body fat changes varied from a small loss to a gain of over 22 lbs. (Kopp-Hoolihan et al., 1999).
Although maternal total energy intake undoubtedly influences maternal fat gain, other biological regulators, such as genetics, insulin, and leptin, probably also play a role. Studies show that maternal genotype influences total weight and, presumably, fat gain. For example, one study found that women who are homozygous for the T allele of the G-protein β3 subunit gain statistically more weight during pregnancy than women with other alleles (Dishy et al., 2003). In another study, polymorphisms of the PPAR-γ2 gene increased weight gain during pregnancy in women with gestational diabetes (Tok et al., 2006). Circulating levels of the hormones insulin and leptin are also associated with excessive amounts of weight gain. In one study, women in the highest quartile for fasting insulin concentrations when they registered for prenatal care had a twofold increased risk for excessive gestational weight gain and a 3.6-fold increased risk of excess weight retained postpartum, suggesting that the excess weight gained was fat (Scholl and Chen, 2002). Higher leptin concentrations at entry for prenatal care have also been found to be associated with excess weight retained postpartum; for each increase in the log of the initial leptin concentration, weight retention increased by 16 lbs. (Stein et al., 1998).
Summary of Biological Predictors
In 1990 the IOM concluded that prepregnancy BMI was a direct determinant of gestational weight gain (Institute of Medicine, 1990). Studies conducted during the intervening 15 years support that conclusion, and also advance understanding of other biological and metabolic factors that may moderate that relationship. Maternal biological factors, such as age, parity, and stature, along with maternal genetic and metabolic state, appear to influence the amount and composition of weight gain.1 The role of other potential metabolic factors that may affect gestational weight gain—such as genetics and hormonal regulators that affect metabolism—remain poorly understood. Future research is needed to identify these factors and to untangle the complex relationships between biological factors and gestational weight gain.
SOCIAL PREDICTORS OF GESTATIONAL WEIGHT GAIN
Naomi Stotland provided an overview of a large body of literature on social predictors of gestational weight gain, including studies from the 1990
IOM report as well as subsequent analyses. This research describes predictors of both inadequate and excessive weight gain. The 1990 report focused on predictors of inadequate gestational weight gain, but more recent attention has focused on predictors of excessive gestational weight gain as a result of concern over obesity.
Recent studies have attempted to isolate social predictors of gestational weight gain by using large samples and collecting measures of multiple potential predictors. Siega-Riz and Hobel (1997) looked specifically at predictors of gestational weight gain below the IOM guidelines in a Hispanic population. For women with low or normal prepregnancy weight, none of the social factors they considered was associated with increased risk of, or actual, insufficient gestational weight gain, but several factors were associated with decreased risk. Among women with low or normal weight, being U.S.-born, being primiparous, being under age 29, having a planned pregnancy, and having a close relative die during the pregnancy decreased the risk of insufficient gestational weight gain. Among the subgroup of women who were overweight or obese at the start of their pregnancies, however, a history of physical abuse increased the risk of low gestational weight gain. Financial support from the fathers of the babies also decreased the risk of low gestational weight gain in this sample.
In a study of mostly black and white participants in the Special Supplemental Nutrition Program for Women, Infants, and Children (WIC), Hickey et al. (1999) found that a short interpregnancy interval, smoking, and late entry into prenatal care were all associated with insufficient gestational weight gain. These associations, however, varied by race/ethnicity and by prepregnancy BMI.
Olson and Strawderman (2003) found that change in the amount of food intake from prepregnancy to pregnancy, change in physical activity from prepregnancy to pregnancy, and smoking behaviors were independently associated with gestational weight gain. Finally, Wells et al. (2006) used PRAMS data from Colorado to show that insufficient gestational weight gain was associated with underweight and obesity, rural residence, low education, and smoking. Excessive gestational weight gain was associated with overweight and obesity and 12 or fewer years of education.
Stotland indicated that numerous studies have examined a wide range of individual characteristics to find possible predictors of gestational weight gain. These include education and socioeconomic status; work and physical activity; caloric intake; overall health status; smoking, alcohol intake, and
substance use; eating disorders; unintended pregnancy; domestic violence; and provider advice. The research on each of these factors is reviewed below.
Education and Socioeconomic Status
Two studies of educational status suggest that lower education is associated with increased risk of insufficient gestational weight gain (Hickey et al., 1999; Wells et al., 2006). Examining socioeconomic status (SES) is more complicated because studies looking at social predictors tend to use cohorts of low-income women only, allowing for little variation in SES. In their study, Olson and Strawderman (2003) reported that women with a family income less than 185 percent of the poverty line were about 2.6 times more likely to have excessive weight gains during pregnancy than women with higher incomes. For the overweight and obese subgroup in the Hispanic cohort studied by Siega-Riz and Hobel (1997), receiving financial support from the baby’s father decreased the risk of insufficient gain during pregnancy. The Colorado PRAMS study (Wells et al., 2006) found no association between SES and the risk of either insufficient or excessive gain during pregnancy. However, the women most at risk, those with no prenatal care, may not be represented in these surveys.
Work and Physical Activity
Work and physical activity were linked to pregnancy outcomes (e.g., low birth weight, prematurity) but not maternal weight in the 1990 IOM report. Data since 1990 are conflicting, generally showing either no difference in gestational weight gain among women with varying amounts of physical activity or showing decreased gain in women with higher physical activity. Two meta-analyses examining a set of heterogeneous studies reported no overall difference in gestational weight gain by physical activity. However, a set of smaller studies has reported reduced gestational weight gain in women who exercised when compared with non-randomized controls. And Olson and Strawderman (2003) found that decreased self-reported physical activity was associated with excessive gestational weight gain.
Before the 1990 IOM report, most studies of caloric intake during pregnancy were supplementation trials conducted in developing countries. These studies generally showed that supplementation resulted in increased gestational weight gain. A number of observational studies of caloric intake
have generally supported this relationship. Olson and Strawderman (2003) used a proxy measure for energy intake by questioning women about changes in the amount of food eaten prior to and during pregnancy. They found that women who ate “much more” during than before their pregnancy had an adjusted odds ratio of 2.35 for excessive weight gain during pregnancy. In a recent prospective observational study conducted in Iceland, Olafsdottir et al. (2006) surveyed a cohort of 406 women with a semiquantitative questionnaire about food frequency that was completed during the women’s second and third trimesters. A higher energy intake in late pregnancy was associated with a lower risk of insufficient gestational weight gain and a higher risk of excessive gestational gain. The researchers also considered both overall energy intake and change in energy intake between the first and second survey points. They found that excessive gain was associated with increased energy intake during that time period, but absolute energy intake in early pregnancy was not associated with gestational weight gain.2
Beyond general food intake, recent studies have also examined consumption of different types of food as well as macronutrient intake. In the Iceland study, the investigators also found that consumption of dairy products and sweets in late pregnancy was associated with a decreased risk of inadequate gain and an increased risk of excessive gain during pregnancy (Olafsdottir et al., 2006). The study by Olson and Strawderman (2003) found that women who consumed three or more servings of fruits and vegetables a day gained 1.81 lbs. less than women who consumed fewer than three servings. A study of adolescents by Stevens-Simon and McAnarney (1992) showed that those who consumed fewer than three snacks a day had slower weight gain during pregnancy.
In a small randomized clinical trial of a low-glycemic versus a high-glycemic diet, Clapp (2002) found that the women on the low-glycemic diet gained less weight during pregnancy (22.9 compared with 40.9 lbs.).3 However, Siega-Riz and Hobel (1997), examining the associations between the glycemic load, race/ethnicity, and gestational weight gain in their cohort of 2,000 pregnant women in North Carolina, reported no statistical effect of
glycemic load4 alone on gestational weight gain. Moreover, they also found that race/ethnicity was associated with prepregnancy weight. During the workshop discussion, Siega-Riz suggested that race/ethnicity may interact with glycemic processes, since in her study white women with higher glycemic load increases are more sensitive to increased weight gain during pregnancy, although this was not true for black women. The Icelandic study found that the percentage of energy intake from various macronutrients is an important predictor of weight gain only among overweight women and late in pregnancy (Olafsdottir et al., 2006). Women who had insufficient gestational weight gain had a lower percentage intake from fat and a higher percentage intake from carbohydrates than women who had optimal or excessive gains.
Overall Health Status
Few studies consider overall health status and gestational weight gain. One study found that chronic or gestational diabetes was associated with increased risk of insufficient gestational weight gain (Brawarsky et al., 2005).
Smoking, Alcohol, and Substance Use
Most studies of smoking published since the 1990 IOM report show an increased risk of inadequate gestational weight gain associated with tobacco use (Furuno et al., 2004; Olson and Strawderman, 2003; Wells et al., 2006). An additional study noted by Calvin Hobel found that smoking status may contribute to the association of parity and the risk of becoming overweight, in that, among smokers, increased risk of high BMI later in life is not associated with parity (Gunderson et al., 2005). Most studies since 1990 of alcohol and illegal substance use show either no association between alcohol use and gestational weight gain or slightly higher gains among drinkers, including adolescents (Stevens-Simon and McAnarney, 1992).
Few studies consider eating disorders and gestational weight gain. One study found no overall difference in gestational weight gain of women with eating disorders compared with a control group, although the anorexic subgroup had a statistically lower mean gain than the controls (Kouba et al., 2005).
Data concerning the effect of unintended pregnancy on gestational weight gain are somewhat conflicting. Hickey et al. (1997) found that mistimed or unplanned pregnancy was associated with an increased risk (adjusted odds ratio) for insufficient gestational weight gain among black women. In the study by Siega-Riz and Hobel (1997), planned pregnancy was associated with a marginally statistically significant decreased risk for insufficient gestational weight gain, but only among the low and normal-weight subjects in this Hispanic cohort. The PRAMS study has not found an association between gestational weight gain and planned pregnancy (Wells et al., 2006).
Two studies of domestic violence suggest an association between intimate partner violence, or domestic violence, and insufficient gestational weight gain (McFarlane et al., 1996; Siega-Riz and Hobel, 1997).
Cogswell et al. (1999) examined the role of professional health care provider advice in influencing gestational weight gain through a mail survey of a predominantly white, middle-class cohort of women. The survey asked how much weight the women were told to gain by their health care provider during pregnancy, their target weight gains, and their actual gain. The study found that the advised and target gains were strongly correlated with actual weight gain. Receiving no advice on gestational weight gain, a fairly prevalent situation, was associated with weight gain outside the guidelines. Provider advice to gain below the IOM recommendations was associated with actual weight gain below the recommendations (an adjusted odds ratio of 3.6), and advice above the guidelines had the same odds ratio for higher rates of gain. The absence of professional health care advice concerning weight gain put women at risk for both too high and too low gains. In this study, black women were more likely to report receiving advice to gain less than the 1990 IOM recommendations.
The increasing prevalence of obesity emphasizes the need to shift focus to predictors of excessive gestational weight gain. The nature and source of provider advice intervention is a research area that could indicate how the role of provider and type of advice influence gestational weight gain.
Stotland highlighted a phenomenon called centering pregnancy or group prenatal care, which gives patients extended time with the provider in a group setting. Although group prenatal care can improve birth weight in women at risk for having low birth weight infants, virtually no research has examined how the type of prenatal care affects gestational weight gain.
Another promising area of future research, concerning the type of provider (midwife versus physician) of care, has not been examined. For example, studies have not yet examined differences between midwives and physicians in providing guidance on prenatal weight gain.
More research is also needed about maternal dietary factors, such as low-glycemic load diets and their association with gestational weight gain. A third area for future research is suggested by the consistent indication of interactions among social factors, race/ethnicity, and rates of gestational weight gain. The presence of such interactions suggests the need to study them further to elucidate the effects of specific social factors on a race/ ethnicity or cultural group. The data are unclear and conflicting concerning the role of physical activity and exercise; more studies are needed of interventions, both during and prior to pregnancy, to improve physical activity. Other potential social factors that may affect gestational weight gain (e.g., hormonal contraception) also remain poorly understood.
Summary of Social Predictors
The initial predictors of gestational weight gain (insufficient or excessive) identified in the 1990 IOM report remain important, but more recent literature has identified several additional predictors, such as unintended pregnancy, eating disorders, physical activity provider advice, and diet. Some potential predictors have not yet been extensively explored (Table 3-1).
The King and Stotland reviews of the contributions of biological/metabolic and social factors to both insufficient and excessive gestational weight gain suggest an intricate web of process and interaction. New data on the predictors of gestational weight gain remain limited in scope. Prepregnancy BMI remains the primary determinant of gestational weight gain, but other biological and metabolic factors probably moderate that relationship. Maternal biological factors, such as age, parity, and stature, along with maternal genetic and metabolic state, appear to influence both the amount and composition of gestational weight gain. Complex interactions among the biological factors influencing gestational weight gain vary widely among different populations of women. Future research could reveal the nature of
TABLE 3-1 Social Predictors of Inadequate and Excessive Gestational Weight Gain
these complex interactions and their influence on the rate and pattern of weight gain during pregnancy.
Numerous social factors are predictors of either inadequate or excessive gestational weight gain. Key social predictors of gestational weight gain include smoking, SES, education, use of illegal substances, diet (which results in biological factors such as energy intake), physical activity, unintended pregnancy, domestic violence, eating disorders, and provider advice. In addition, the literature suggests other potential social predictors—type of provider and type of prenatal care—that deserve consideration. The literature on racial/ethnic differences in these biological and social predictors is limited.
This review of both biological and social factors of gestational weight gain illustrates factors that may impede or foster compliance with recommended gestational weight guidelines and may guide Title V maternal and child health programs in helping women of childbearing age to achieve and maintain recommended weight before, during, and after pregnancy. Recent research suggests that narrowing the range of recommended gestational weight gain values may be especially important for overweight or obese women. However, it is unclear whether women would respond to such a
change, since a high proportion of women gain in excess of current recommended guidelines.
Abrams, B., and Parker, J.D. 1990 Maternal weight gain in women with good pregnancy outcome. Obstetrics and Gynecology 76:1–7.
Brawarsky, P., Stotland, N.E., Jackson, R.A., Fuentes-Afflick, E., Escobar, G.J., Rubashkin, N., and Haas, J.S. 2005 Pre-pregnancy and pregnancy-related factors and the risk of excessive or inadequate gestational weight gain. International Journal of Gynaecology and Obstetrics 91(2):125–131.
Butte, N.F., Ellis, K.J., Wong, W.W., Hopkinson, J.M., and O’Brian Smith, E. 2003 Composition of gestational weight gain impacts maternal fat retention and infant birth weight. American Journal of Obstetrics and Gynecology 189:1423–1432.
Carmichael, S., Abrams, B., and Selvin, S. 1997 The pattern of maternal weight gain in women with good pregnancy outcomes. American Journal of Public Health 87:1984–1988.
Clapp, J.F. III. 2002 Maternal carbohydrate intake and pregnancy outcome. Proceedings of the Nutrition Society 61(1):45–50.
Cogswell, M.E., Scanlon, K.S., Fein, S.B., and Schieve, L.A. 1999 Medically advised, mother’s personal target, and actual weight gain during pregnancy. Obstetrics and Gynecology 94(4):616–622.
Dietz, P.M., Callaghan, W.M., Cogswell, M.E., Morrow, B., Ferre, C., and Schieve, L.A. 2006 Combined effects of prepregnancy body mass index and weight gain during pregnancy on the risk of preterm delivery. Epidemiology 17:170–177.
Dishy, V., Gupta, S., Landau, R., Xie, H.G., Kim, R.B., Smiley, R.M., Byrne, D.W., Wood, A.J., and Stein, C.M. 2003 G-protein b3 subunits 825 C/T polymorphism is associated with weight gain during pregnancy. Pharmacogenetics 13:241–242.
Furuno, J.P., Gallicchio, L., and Sexton, M. 2004 Cigarette smoking and low maternal weight gain in Medicaid-eligible pregnant women. Journal of Women’s Health 13(7):770–777.
Gunderson, E.P., Quesenberry, C.P., Lewis, C.E., Tsai, A.L., Sternfeld, B., West, D.S., and Signey, S. 2004 Development of overweight associated with childbearing depends on smoking habit: The Coronary Artery Risk Development in Young Adults (CARDIA) study. Obesity Research 12(12):2041–2053.
Harris, H.E., Ellison, G.T.H., and Holliday, M. 1997 Is there an independent association between parity and maternal weight gain? Annals of Human Biology 24:507–591.
Hediger, M.L., School, T.O., Ances, I.G., Belsky, D.H., and Salmon, R.W. 1990 Rate and amount of weight gain during adolescent pregnancy: Associations with maternal weight-for-height and birth weight. American Journal of Clinical Nutrition 52:793–799.
Hickey, C.A., Cliver, S.P., Goldenberg, R.L., McNeal, S.F., and Hoffman, H.J. 1997 Low prenatal weight gain among low-income women: What are the risk factors? Birth 24(2):102–108.
Hickey, C.A., Kreauter, M., Bronstein, J., Johnson, V., McNeal, S.F., Harshbarger, D.S., and Woolbright, L.A. 1999 Low prenatal weight gain among adult WIC participants delivering term singleton infants: Variation by maternal and program participation characteristics. Maternal and Child Health Journal 3(3):129–140.
Howie, L.D., Parker, J.D., and Schoendorf, K.C. 2003 Excessive maternal weight gain patterns in adolescents. Journal of the American Dietetic Association 103(12):1653–1657.
Hytten, F., and Chamberlain, G. 1980 Clinical Physiology in Obstetrics. Oxford, Eng.: Blackwell Scientific Publications.
Institute of Medicine 1990 Nutrition During Pregnancy. Washington, DC: National Academy Press.
Johnston, C.S., Christopher, F.S., and Kandell, L.A. 1991 Pregnancy weight gain in adolescents and young adults. Journal of the American College of Nutrition 10:185–189.
Kopp-Hoolihan, L.E., Van Loan, M.D., Wong, W.W., and King, J.C. 1999 Fat mass deposition during pregnancy using a four-component model. Journal of Applied Physiology 87:196–202.
Kouba, S., Hallstrom, T., Lindholm, C., and Hirschberg, A.L. 2005 Pregnancy and neonatal outcomes in women with eating disorders. Obstetrics and Gynecology 105(2):255–260.
McFarlane, J., Parker, B., and Soeken, K. 1996 Abuse during pregnancy: Associations with maternal health and infant birth weight. Nursing Research 45(1):37–42.
Olafsdottir, A.S., Skuladottier, G.V., Thorsdottir, I., Hauksson, A., and Steingrimsdottir, L. 2006 Maternal diet in early and late pregnancy in relation to weight gain. International Journal of Obesity 30(3):492–499.
Olson, C.M., and Strawderman, M.S. 2003 Modifiable behavioral factors in a biopsychosocial model predict inadequate and excessive gestational weight gain. Journal of the American Dietetic Association 103(1):48–54.
Scholl, T.O., and Chen, X. 2002 Insulin and the “thrifty” woman: The influence of insulin during pregnancy on gestational weight gain and postpartum weight retention. Maternal and Child Health Journal 6:255–261.
Siega-Riz, A.M., and Adair, L.S. 1993 Biological determinants of pregnancy weight gain in a Filipino population. American Journal of Clinical Nutrition 57:365–372.
Siega-Riz, A.M., and Hobel, C.J. 1997 Predictors of poor maternal weight gain from baseline anthropometric, psychosocial, and demographic information in a Hispanic population. Journal of the American Dietetic Association 97:1264–1268.
Stein, T.P., Scholl, T.O., Schluter, M.D., and Schroeder, C.M. 1998 Plasma leptin influences gestational weight gain and postpartum weight retention. American Journal of Clinical Nutrition 68:1236–1240.
Stevens-Simon, C., and McAnarney, E.R. 1992 Determinants of weight gain in pregnant adolescents. Journal of the American Dietetic Association 92(11):1348–1351.
Stevens-Simon, C., McAnarney, E.R., and Roghmann, K.J. 1993 Adolescent gestational weight gain and birth weight. Pediatrics 92(6):805–809.
Stotland, N.E. 2006 Gestational Weight Gain: Social Predictors or Relationships. Presentation at the Workshop on the Impact of Pregnancy Weight on Maternal and Child Health, May 30, Washington, DC.
Tok, E., Ertunc, D., Bilgin, O., Erdal, E., Kaplanoglu, M., and Dilek, S. 2006 PPAR-gamma2 Pro12Ala polymorphism is associated with weight gain in women with gestational diabetes mellitus. European Journal of Obstetrics Gynecology and Reproductive Biology May:E-pub.
Wells, C.S., Schwalberg, R., Noonan, G., and Gabor, V. 2006 Factors influencing inadequate and excessive weight gain in pregnancy: Colorado, 2000–2002. Maternal and Child Health Journal 10(1):55–62.
Wolfe, W.S., Sobal, J., Olson, C.M., Frongillo, E.A., and Williamson, D.F. 1997 Parity-associated weight gain and its modification by sociodemographic and behavioral factors: A prospective analysis in U.S. women. International Journal of Obesity Related Metabolic Disorders 21(9):802–810.