Racial-Ethnic Differences in Pregnancy-Related Weight^,

Abstract

This review examines published literature to answer 2 questions: 1) Are there racial-ethnic differences in excessive or inadequate gestational weight gain (GWG) and postpartum weight retention (PPWR)? and 2) Is there evidence that approaches to promote healthy weight during and after pregnancy should vary by race-ethnicity? We identified a limited number of articles that explicitly looked at racial-ethnic differences in either GWG or PPWR after controlling for relevant covariates. These studies suggest that black and Hispanic women are more likely to gain inadequately based on the Institute of Medicine’s pregnancy weight gain guidelines compared to white women. Black women are more likely to retain considerable amounts of weight postpartum compared to both Hispanic and white mothers. Studies were inconclusive as to whether Hispanic women retained more or less weight postpartum, so more research is needed. Interventions to increase GWG were few and those designed to reduce GWG and PPWR showed mixed results. Future studies should address the methodological and conceptual limitations of prior research as well as investigate biological mechanisms and behavioral risk factors to determine the reasons for the racial-ethnic differences in pregnancy-related weight outcomes. Interventions would benefit from a mixed-methods approach that specifically identifies race-relevant barriers to weight management during and after pregnancy. Attention to the greater social context in which pregnancy-related weight exists is also needed.

Introduction

Racial-ethnic differences exist in the US for several maternal and child health outcomes. Black, Puerto Rican, and American Indian/Alaska Native women continue to have considerably higher rates of infant mortality compared to white women (Fig. 1) (1). Black women in particular have a greater risk for low birth weight (Fig. 2), preterm birth, stillbirth, and maternal mortality compared to white or Hispanic U.S. mothers (2). Childhood and adolescent obesity is also more prevalent in black, Hispanic, and American Indian/Alaska Natives compared to whites (Fig. 3) (3, 4). These health differences are due in part to the disproportionate obesity epidemic among racial-ethnic groups in the US; whereas 35% of all women > 20 y old are obese, the prevalence is higher for black (50%) and Hispanic (43%) women; similar trends are seen among childbearing women 20–39 y old (2).

Figure 1.

Infant mortality rates by race-ethnicity, United States, 2000 and 2007. Source: Table B: Infant, neonatal, and postneonatal mortality rates, by race and Hispanic origin of mother: United States, 1995, 2000–2007 linked files. Federal Interagency Forum on Child and Family Statistics. America’s children: key national indicators of well-being, 2011. Washington, DC: U.S. Government Printing Office; 2011 [cited 2011 Aug 8]. Available from: http://www.cdc.gov/nchs/data/nvsr/nvsr59/nvsr59_06.pdf.

Figure 2.

Percent low birth weight births by race-ethnicity, 2007. Source: Table 5. Percentage of live births with selected maternal and infant characteristics, by Hispanic origin of mother and race of mother for mothers of non-Hispanic origin: United States, 2007 linked file. Federal Interagency Forum on Child and Family Statistics. America’s children: key national indicators of well-being, 2011. Washington, DC: U.S. Government Printing Office; 2011 [cited 2011 Aug 8]. Available from: http://www.cdc.gov/nchs/data/nvsr/nvsr59/nvsr59_06.pdf.

Figure 3.

Prevalence of high BMI among U.S. adolescent girls age 12–19 years old based on BMI percentile of CDC growth charts by race-ethnicity, 2003–2006. Source: Tables 2–8 (2). [Adapted with permission from (2)].

Maternal GWG⁶ contributes to the racial-ethnic differences in health outcomes. Both inadequate and excessive GWG may negatively influence the fetal environment during key developmental windows of metabolic and epigenetic plasticity contributing to later life chronic disease in the offspring (5). A recent systematic review examined the 1990 IOM GWG recommendations and reported strong evidence for associations between inadequate GWG and small for gestational age as well as excessive GWG and large for gestational age (6). This review of 35 studies found moderate evidence for the association between excessive GWG and PPWR; it also considered evidence linking excessive GWG and childhood obesity. Based on the findings from the review, the IOM GWG guidelines were revised and released in 2009 (2). The 1990 and 2009 IOM GWG recommendations are shown in Table 1.

Table 1.

IOM recommended amounts of GWG in 1990 and 2009 by weight class¹

Prepregnancy BMI	1990 IOM standards2		2009 IOM standards3
	BMI	Total weight gain range	BMI	Total weight gain range
	kg/m2	kg	kg/m2	kg
Underweight	<19.8	13–18	<18.5	13–18
Normal Weight	19.8–26.0	11–16	18.5–24.9	11–16
Overweight	>26.0–29.0	7–11	25.0–29.9	7–11
Obese	>29.0	≥7	≥30.0	7–9

¹GWG, gestational weight gain; IOM, Institute of Medicine. [Adapted with permission from (2, 29)].

²Based on 1959 Metropolitan Life Insurance Company’s weight-for-height standards.

³Based on WHO standards.

Despite the IOM GWG recommendations, 21.2% of women participating in the PNSS in 2009 gained inadequately and 48.2% gained excessively (7). Furthermore, the percentage of women gaining outside of the recommended range has increased over time (2). Prepregnancy BMI category is the most important risk factor for excessive gain above the IOM ranges. Compared to women with a normal BMI, those who begin pregnancy overweight or obese are more likely to gain excessively, whereas underweight women tend to gain inadequately (8).

Over the last 25 y, the proportion of births to non-white mothers increased, particularly among Hispanics, who comprise over 20% of all U.S. births (2). The increasing racial-ethnic differences in U.S. births, maternal obesity, adverse fetal outcomes, and childhood obesity highlight the importance of understanding maternal race-ethnicity as a risk factor for extremes of GWG and PPWR and if tailored interventions are needed. In this review, we examine published studies that compared minority U.S. women to white women to answer 2 questions: 1) Are there racial-ethnic differences in excessive or inadequate GWG and PPWR? and 2) Is there evidence that race-ethnicity specific approaches are needed to promote healthy weight during and after pregnancy? We carried out a comprehensive literature review by searching PubMed for studies published between 1990 and 2011 using the following keywords: GWG, pregnancy, obesity, race, black, Hispanic, disparities, postpartum. We also examined reference lists for the papers we found. We then selected studies that compared white women with black and/or Hispanic women, the race-ethnic groups most represented in research studies. We eliminated studies of women with pregnancy complications (e.g. diabetic or hypertensive) and emphasized studies that report GWG based on maternal prepregnancy BMI status, as highlighted in the IOM report. Finally, we describe gaps and methodological issues in the literature and propose future research directions to address racial-ethnic differences in pregnancy-related weight.

Current status of knowledge

Pregnancy-related weight definitions

Over the past 20 y, the 1990 IOM pregnancy guidelines have been used to define low, adequate, and excessive GWG in research studies; more recent studies reference the revised 2009 guidelines (2) (Table 1). PPWR is usually defined as weight change after delivery minus prepregnancy weight; however, the definition varies by time after birth as well as method of expression [e.g. an absolute value, a defined cut point such as 4.5 or 9 kg (10 or 20 lbs), or continuous BMI units (mean/SD)] (2). The systematic review of the evidence linking GWG and health outcomes commissioned by the Agency for Healthcare Research and Quality classified studies into 3 categories of PPWR based on time since delivery: short term (<11 wk), intermediate (3 mo to 3 y), and long term (>3 y) (6). In this review, we emphasized studies of intermediate PPWR, because of the 3 categories it is most strongly linked to GWG (6). Short-term PPWR may not allow adequate time for women to lose weight and long-term PPWR is confounded by inter-pregnancy weight gain or gain related to aging (8). A recent review suggests that the expression “postpartum weight” be limited to follow-up times of 12–18 mo (9). Currently, no standard definition for PPWR exists, which makes comparing study results difficult.

Data sources for pregnancy-related weight

Several large U.S. studies that reported weight during and after pregnancy provided the prevalence of inadequate and excessive GWG and PPWR by race-ethnicity and inform the discussion of risk factors in this review (Table 2). Four of the studies include national samples: the PNSS (10) and PRAMS (11, 12) are ongoing studies conducted by the U.S. CDC; the IFPS I and II were a collaboration between the U.S. FDA, CDC, and other federal agencies (13, 14); and the NMIHS was conducted by the National Center for Health Statistics (15, 16). The NMIHS was the only nationally representative study consisting of weighted data; the other 3 studies included a subset of states in their sampling frame, focused on low-income women, or had a higher response rate of higher income women. Three cohorts, the PIN in North Carolina (17–19), Project VIVA in Boston (20–23), and the Austin New Mothers Study in Texas (24, 25), also provided important insights into pregnancy-related weight outcomes. These studies used prospectively collected, measured maternal weights, and a wide variety of demographic, behavioral, and psychosocial variables that are potential risk factors for extremes in GWG. However, these studies had smaller sample sizes than the national samples, which limited stratification by prepregnancy BMI and race-ethnicity.

TABLE 2.

Data sources for pregnancy-related weight outcomes comparing racial-ethnic differences

Study	Participant recruitment	Measured GWG?	Time at measurement	Racial-ethnic differences (%)		Measured PPWR?	Time at measurement	Racial-ethnic differences	Risk factors studied
PNSS	1979- Present	Yes	Ongoing: first prenatal visit of WIC participants	Low: White: 18.4 Black: 23 Hispanic: 23.5	High: White: 52.6 Black: 48.3 Hispanic: 43.1	Yes	Ongoing pp follow-up of WIC participants	Mean weight retained: White: 7 lbsBlack: 13 lbs Hispanic: 12 lbs	—
Caulfield et al.	1987–1989	Yes	Postdelivery record extraction	Low: White: 24.8 Black: 38.3 OR: 1.51*	High: White: 43.0 Black: 33.6 OR: 0.89	No	—	—	Smoking, parity, education, prepregnancy BMI, gestational hypertension, age
NMIHS	1988	Yes	10–18 mo after delivery	Low: White: 21 Black: 34	NR	Yes	10–24 mo pp; 10–18 mo pp	>9 kg (20 lbs) retained: White: 8.2% Black: 21.6% OR: 2.20*	SES, education, income, marital status, parity, GWG, prepregnancy BMI, age, breastfeeding, infant weight
IFPS I & II	1993 2005–2006	Yes	Women < 3 mo from delivery	NR	NR	No	—	—	Provider advice
Boardley et al.	NR	No	—	—	—	Yes	7–12 mo pp	Black vs white: 2.9-kg (6.4-lb) increase in weight change compared to white mothers	Education, marital status, parity, GWG, prepregnancy BMI, age, employment, breastfeeding, energy intake, depression, contraceptive use, smoking, diet, physical activity, infant birth weight
Hickey et al.	1994	Yes	Postdelivery record extraction	Low: White: 27.7 Black: 34.6 OR: 1.39	NR	No	—	—	Education, partnership, anemia, prepregnancy BMI, parity, inter-pregnancy interval, tobacco/alcohol use, prenatal care
PIN	1995–1999 2002–2005	Yes	24–29 wk gestation 27–30 wk gestation < 20 wk gestation	NR	NR	Yes	3 and 12 mo pp	>4.5kg (10 lbs) retention: White: 64.8%Black: 22.1%OR: 1.8	Diet, body image, food insecurity, depression, stress, locus of control, neighborhood physical incivilities, social spaces, territoriality, education, income, marital status, GWG, prepregnancy BMI, sleep, infant hospitalization, eating disorder, age, employment status, breastfeeding, energy intake, physical activity, provider advice
ANMS	1999–2001	No	—	—	—	Yes	Delivery, 6 wk, 3 mo, 6 mo, and 12 mo pp	“...the change in BMI from 3 mo to 6 mo and from 6 mo to 12 mo in the White group is significantly different from the change in the other two [Black and Hispanic].” (25)	Education, marital status, parity, GWG, prepregnancy BMI, age, breastfeeding, energy intake, depression, contraceptive use, weight-related distress, body image
Project Viva	1999–2002	Yes	<22 wk gestation	Low: White: 47.7 Black: 51.4 Hispanic: 56.0	High: White: 52.3 Black: 48.6 Hispanic: 44.0	Yes	6 and 12 mo pp	>5 kg (11 lbs) retention: White: 63% Black: 19% Hispanic: 6% (23) white vs. non-white OR: 2.71 (22)	Diet, physical activity, smoking, employment, depression, parity, education, prepregnancy BMI, age, income, marital status, GWG, sleep, energy intake, physical activity
Rothberg et al.	2001–2004	Yes	16–24 wk gestation	“White…women were most likely to exceed gestational weight gain guidelines across BMI categories…”		Yes	6 and 12 mo pp	“White…women retained the most postpartum…”“Black women showed similar trajectories, but..[lost] more weight in the postpartum period.” “Hispanic women showed the most favorable trajectories overall.”	Smoking, employment, depression, stress, partnership, parity, prepregnancy BMI, gestational hypertension, age, breastfeeding, contraceptive use, inter-pregnancy period
PRAMS	2004–2005	Yes	2–4 mo after delivery	Low (<6.8 kg): White: 13.3 Black: 21.7 Hispanic: 17.3	High (>20.4 kg): White: 16.6 Black: 15.1 Hispanic: 12.1	No	—	—	Parity, education, prepregnancy BMI, gestational hypertension, age
Nuss et al.	NR	No	—	—	—	Yes	Immediately postdelivery and 12 mo	NR	Nutrition knowledge

ANMS, Austin New Mothers Study; GWG, gestational weight gain; IFPS, Infant Feeding Practices Study; NMIHS, National Maternal and Infant Health Survey; NR, not reported; PIN, Pregnancy, Infection, and Nutrition Study; PNSS, Pregnancy Nutrition Surveillance System; pp, postpartum; PPWR, postpartum weight retention; PRAMS, Pregnancy Risk Assessment Monitoring System; SES, socioeconomic status; WIC, Women, Infants and Children Food and Nutrition Services.

GWG

Nationally representative data indicate racial-ethnic differences in the prevalence of GWG based on prepregnancy BMI. Figure 4 shows unadjusted proportions of women, by race-ethnicity, who gained above and below the 2009 IOM GWG recommendations in the PNSS, which represents over 1.3 million low-income women from 31 states, the District of Columbia, 5 tribal governments, and 1 U.S. territory in 2009. More than 50% of white, American Indian, and multi-race women gained excessively compared to 48, 43, and 33% of black, Hispanic, and Asian women, respectively (7). Inadequate GWG was most prevalent among Asian (26.6%) and Hispanic and black mothers (∼23% each) compared to 18.4% in non-Hispanic white women. A multivariable-adjusted analysis of >52,000 women who participated in the 2004–2005 PRAMS confirmed that Hispanic, black, and “other” women gain significantly less weight than whites after adjusting for prepregnancy BMI, age, parity, and education (12). Reports of multivariable-adjusted analyses of both national studies and smaller cohorts since 1980 confirm that black (26, 27) and Hispanic women (20, 28) compared to white women are more likely to have inadequate weight gain as opposed to excessive GWG. Although there is no racial-ethnic difference in excessive GWG, it is concerning that >40% of black and Hispanic women have excess GWG. Thus, future interventions that target both excessive and inadequate GWG in minority groups may reduce adverse outcomes.

Figure 4.

Trends in GWG based on 2009 IOM guidelines by race-ethnicity. Reproduced from (7).

Interestingly, the 1990 IOM GWG committee recommended that black women gain at the upper end of their BMI-recommended GWG range (29). The basis for this recommendation was the persistent rates of low birth weight and infant mortality in black women and evidence that black women were more likely to gain inadequately during pregnancy. However, subsequent reports of analyses of the PNSS provided no evidence that gaining at the upper end of the 1990 IOM recommendations reduced low birth weight in black women (30). Therefore, the 2009 IOM revision does not suggest modifications in the GWG recommendations by race-ethnicity; studies published since then found little evidence that the relationship between GWG and fetal outcomes differs between white and black women (31, 32).

PPWR

To estimate the overall prevalence of PPWR, the 2009 IOM report examined crude measured weight data at a visit > 24 wk after birth from 49,000 PNSS women. Almost one-half of the women retained >4.5 kg (10 lbs) and one-quarter retained >9 kg (20 lbs). In contrast, 12-mo follow-up data from the federally funded IFPS II, a longitudinal study of 4000 women, suggest that approximately one-quarter of women retained >4.5 kg and 12% >9 kg at 1 y postpartum (2). The low-income and diverse PNSS sample represents only a small fraction of the PNSS data set for that year, because the majority of these women were weighed much earlier in the postpartum period. The IFPS II sample is primarily white and more highly educated than the U.S. population. Despite differences in sample composition, both studies found that excessive GWG was associated with higher prevalence of excess maternal PPWR for all prepregnancy BMI groups (2).

A comparison by race-ethnicity was only possible for data from PNSS; compared to white and Hispanic women, a higher proportion of black women retained 9 kg at >24 wk after birth regardless of their prepregnancy weight or GWG category. Racial-ethnic differences were less striking for retention of 4.5 kg (2). Several studies demonstrate that this black-white difference in PPWR persists after adjusting for covariates (16, 17, 24, 33), whereas adjusted data examining differences between white and Hispanic women are inconclusive (25, 28).

Is there evidence that successful approaches to promote healthy weight during and after pregnancy should vary by race-ethnicity?

Observational data

GWG.

Reasons for inadequate GWG in minority women are not well understood for 2 reasons: 1) few definitive risk factors for low GWG have been identified regardless of race-ethnicity (2); and 2) studies of inadequate or excessive GWG have adjusted for, rather than stratifying by, race-ethnicity. We identified only 2 studies that directly examined whether risk factors for inadequate GWG varied between black and white mothers and both were conducted >16 y ago. Caulfield et al. (27) studied a sample of 2617 black and 1253 white women who delivered at Johns Hopkins Hospital between 1987 and 1989; after adjusting for parity, education, height, prepregnancy BMI, fetal gender, smoking, gestational age, and hypertension, black women were significantly more likely than whites to have inadequate GWG [OR 1.51 (95% CI = 1.23, 1.85)]. There was no evidence of effect modification and the authors concluded that risk factors for inadequate GWG did not vary by race-ethnicity (27). Hickey et al. (34) reported similar findings in the Alabama WIC program in 1994, with black women more likely to have inadequate GWG. After adjusting for trimester of prenatal care and WIC certification, inter-pregnancy interval, alcohol and tobacco use, anemia, marital status, parity, gestational age, and maternal education, the OR for inadequate GWG in black compared to white women was 1.34 (95% CI = 1.28, 1.50). Though risk factors were modeled separately by race-ethnicity in stratified models, formal tests for interaction were not reported and authors did not conclude any differences by race-ethnicity. Taken together, these studies do not provide insight into why black women are at higher risk for inadequate GWG.

PPWR.

We identified few studies that directly examined whether risk factors for PPWR varied by race-ethnicity. Data from the 1988 NMIHS showed that prepregnancy BMI and high prenatal weight gain were important predictors of PPWR for both racial-ethnic groups. However, having a partner and low SES were associated with increased PPWR only in white mothers, whereas high multiparity and medium SES were important predictors of high PPWR only in black mothers (16). In a 1995 study of 345 low-income white and black South Carolina WIC participants 7–12 mo postpartum, after adjusting for covariates, race-ethnicity was associated with a 2.9-kg (6.4-lb) increase in PPWR for black compared to white mothers (33). Prepregnancy weight and parity predicted PPWR in both black and white women, but prenatal physical activity predicted higher PPWR in black women and lower PPWR in white women. Though crude measures of energy and fat intake were higher and postpartum physical activity was lower in black compared to white mothers, after adjustment, these variables were unrelated to PPWR.

An apparent paradox exists whereby black women are at higher risk for both inadequate GWG (which is associated with low birth weight) and excessive adiposity after birth (for which inadequate GWG is usually protective) (15, 16). The mechanism for excess PPWR is poorly understood, particularly in black women; possibilities include true “retention” of GWG due to lack of weight loss compared to weight gain after birth. Several other studies suggest differences in weight loss after birth by race-ethnicity (25, 28).

Experimental data

GWG.

To address the health risks associated with inadequate or excessive GWG, the 2009 IOM GWG report recommended that “those who provide prenatal care to women should offer counseling, such as guidance on dietary intake and physical activity that is tailored to their life circumstances” (2). Most pregnant women want to have healthy babies and thus may be more motivated to change their behavior during pregnancy than at other times (35). Intervention during pregnancy could potentially improve weight management behaviors and long-term health for the woman and her family. The multiple prenatal care visits offer consistent contact with the health care system, which provides an ideal vehicle for delivery of behavioral interventions to women. However, current prenatal care services do not provide such interventions and this is unlikely to change without convincing research-based evidence that effective intervention strategies can promote healthy GWG in the clinical setting.

Inadequate GWG

Although minority women are more likely to gain inadequately and inadequate gain is associated with reduced birth size, the 1990 IOM report reviewed trials aimed at increasing GWG in primarily undernourished women and found little evidence that interventions were effective. They called for new research to test the effectiveness of interventions to improve GWG, but we did not identify any studies published since then (29).

Excessive GWG

There is a growing body of evidence aimed at decreasing excessive GWG. In the past year, 6 critical literature reviews comprised of ∼12 controlled trials investigated how behavioral interventions to improve maternal dietary intake and/or physical activity reduce excess GWG. Intervention strategies include counseling and education about GWG, healthy eating, physical activity, and/or monitoring of weight gain, with or without feedback. The intensity and frequency of interventions and the number and combination of different components varied. One review focused only on women who began pregnancy overweight or obese (36) and 5 included a wider range of prepregnancy BMI (37–41). Three groups conducted meta-analysis (37, 39, 41) and 3 were systematic reviews. Conducted in Australia, Europe, and the United States, trial sample sizes ranged from 41 to 560. Though all reviews used high quality methodology to assess the evidence and all looked at the same accumulation of data, 3 of the reviews concluded that interventions can effectively reduce GWG, though results were inconsistent (38, 40, 41), 2 concluded that interventions are ineffective (36, 37), and 1 concluded that the quality of the studies was too weak to consider their findings for evidence-based guidelines (39). Results varied by subgroups (38, 40–42), but no trial to date to our knowledge has investigated the need to tailor interventions by race-ethnicity. Overall, studies with stronger study designs, follow-up of women into the postpartum period, collection of detailed data on intermediate behaviors and body composition, and adequate statistical power to investigate maternal metabolic markers as well as offspring outcomes are needed.

We identified one small, randomized intervention study conducted in a racially and ethnically diverse population (∼40% African American, 23% Latina, and 13% Indian) (43). This intervention reduced GWG in obese, low-income women through intensive counseling from a dietitian and the requirement that all food consumed daily be recorded in a diary. The recently published Fit for Delivery Study was also somewhat diverse (∼20% Hispanic and 8% black) and effectively reduced excessive GWG in the normal but not the overweight/obese prepregnancy BMI group (44). Neither study had sufficient participants to evaluate effectiveness by race-ethnicity.

PPWR.

The Fit for Delivery Study also reported that the GWG intervention significantly increased the proportion of both prepregnancy normal and overweight/obese women who returned to their prepregnancy weight at 6 mo after birth, despite the fact that no additional intervention was offered postpartum (44). A recent review of 6 postpartum studies was also optimistic in concluding that postpartum diet and exercise-focused experimental studies improved maternal fitness and body composition (45). However, Kuhlmann et al. (46) found that only 2 small randomized postpartum trials of diet and physical activity met inclusion criteria for their recent review, and although both studies effectively reduced postpartum weight at 6 mo or 1 y, reviewers noted high attrition and other methodological problems. The Active Mothers Postpartum Trial, a recent randomized trial of 450 North Carolina women, offered counseling and classes from 6 wk to 1 y postpartum to modify maternal diet and physical activity in a study group that was, on average, highly educated, married, and diverse; 45% of the participants were black (47). This intervention produced no significant differences in maternal weight, diet, or activity in the entire sample or when data were examined separately by race-ethnicity. A secondary analysis suggested that postpartum weight loss increased with more class attendance, and the authors attributed the null findings to low participation in classes due to competing demands such as childcare, work, and school (47). Walker (48) recently published an exploration of responses to ethnic-specific, 13-wk postpartum weight interventions in 71 low-income women in Texas. There were no significant differences in weight loss between intervention and control groups, but body dissatisfaction was significantly decreased with intervention in the white group and weight distress was significantly decreased among Hispanics. For the black group, lower perceived stress at baseline was associated with greater weight loss, whereas higher perceived stress was associated with weight gain. This small study, supplemented with follow-up interviews to identify differences in women’s responses to attempted weight loss, echoed barriers to participation raised in the Active Mothers Postpartum Trial and provides a model for future studies to inform interventions (48). Data from the Fit for Delivery Study also suggest that interventions during pregnancy may be more effective than those that begin after the baby is born (44).

Qualitative studies

Given the low success of interventions to manage GWG and PPWR, qualitative studies such as focus groups or in-depth interviews can provide insights for designing new interventions. For example, focus groups conducted in the PIN study found that whereas pregnant women of all racial-ethnic backgrounds tended to report the same barriers to physical activity, including fatigue, low energy, and childcare/household responsibilities, Hispanic women also reported more social isolation due to transportation and language barriers (49). Another small focus group study of Latina (Puerto Rican and Dominican) women concluded that most of the whites and Latinas in the sample identified similar barriers and motivators to physical activity (50).

Focus groups of nonpregnant, obese, black women indicated that the perinatal period was a time when permanent weight problems began (51). Work by Davis et al. (51) suggests important race-specific factors to consider in tailoring weight-loss interventions. Black obese women expressed interest in psychological and spiritual approaches with a focus on food characteristics rather than physical activity, whereas white obese women also expressed concern about emotional and psychological aspects but preferred emphasis on physical activity. Furthermore, black women also identified their African American subculture (e.g. cultural foods, setting, and social interactions) as a hindrance to successful weight management (52). Such cultural factors have been used to tailor interventions to address weight loss in this group (53–55).

Focus groups of low-income minority women suggest that despite a strong desire to lose weight postpartum, women identify obstacles including the need for a structured program tailored to their lifestyle and increased social support by the entire family (56, 57). These women describe family food preferences as obstacles to healthy food choices and a sense of hopelessness with lack of success in weight loss that causes overeating and rebound weight gain (56, 57). Addressing psychosocial barriers in addition to the general barriers of cost, lack of convenience, and childcare responsibilities might improve overall effectiveness of interventions. Input from relevant stakeholders is critical for obtaining guidance to develop successful interventions (58), but data are insufficient to determine whether interventions require tailoring by race-ethnicity, SES, or other factors.

Conclusion and future directions

Our review indicates that GWG and PPWR are linked to a number of adverse maternal and child health outcomes, which vary by race-ethnicity. The studies discussed confirm that the prevalence of inadequate GWG and excessive PPWR are greater in minority women, whereas the prevalence of excessive GWG is greater among white women. However, >40% of minority women do gain above the 2009 IOM upper recommended limit, which continues to be an important health concern. We identified limited observational and experimental data to determine whether minority women require different approaches to optimize GWG and PPWR.

To move the field forward it is important to understand and build upon the current literature base. Future translational studies conducted by multidisciplinary teams of basic, clinical, and population sciences are needed. We suggest that the following methodological issues must be addressed.

Sample size number and composition

Studies must be large enough to allow joint consideration of race-ethnicity, prepregnancy BMI, categories of GWG adequacy, SES, and maternal and offspring outcomes. As pointed out in this review, the vast majority of studies simply adjust for race-ethnicity rather than examining differences in risk factors or effectiveness by subgroups. To enhance recruitment and retention of representative samples of minority women, future studies should focus on understanding the unique barriers to participating in research studies that minority pregnant and postpartum women face. This is especially important for clinical trials, where historical mistrust may still affect minority women’s decisions to participate in research (59, 60).

Race-ethnicity, nativity, and SES

When conceptualizing mechanisms for the racial-ethnic differences in childbearing factors related to long-term obesity, race extends beyond its biological definition and is thought to be a marker for disproportionate social and cultural exposures that affect health (61). Current definitions of racial-ethnic groups used in the literature, however, are too broad to capture the impact of these differences. For example, in many studies, “Hispanic” or “Latino” is used to categorize a range of different ethnicities, including Mexican American, Puerto Rican, Cuban, and Dominican. The wide culture variation across these groups is washed out when they are aggregated into one. This problem persists in the categorization of “black” women, because U.S.-born African American women have different cultural backgrounds and experiences than Caribbean or African immigrants from various countries. In both situations, immigrant status is also not accounted for, thus camouflaging the impact of acculturation on weight management and pregnancy outcomes.

African American and other racial-ethnic minorities are more likely to live in poverty compared to white women; inadequate control for SES indicators and other indicators of the broader social context may overestimate associations between race-ethnicity and health outcomes. Emerging research is beginning to document that racial-ethnic differences in health outcomes such as obesity are minimized when comparing racial-ethnic groups with similar SES and exposed to similar social environments (e.g. living in integrated communities) (62, 63). To attempt to disentangle race and SES as well as consider a comprehensive set of socio-contextual variables (61), future studies of pregnancy-related weight differences should carefully define race-ethnicity, including nativity, and pay close attention to individual and population level SES (64).

Measurement of pregnancy-related weight

Researchers rely on maternal recall of prepregnancy weight, because clinically measured prepregnancy weights are usually unavailable. Using measured early pregnancy weight as the anchor reduces error due to maternal report but ignores weight gained since the pregnancy began. Self-reported weight and height contribute to measurement error in the calculation of prepregnancy BMI and misclassification into BMI categories, which affect estimates of GWG and PPWR (65). Measurement of repeated maternal weights from preconception through 1 y postpartum is critical in future research. The growing use of electronic medical records will increase the availability of clinically documented weights in the future.

It is also important to note that, although the majority of studies used the 1990 IOM guidelines to assess GWG adequacy (13, 15, 17, 18, 20–22, 24, 25, 27, 30, 34, 44, 66–70), some of the more recent studies used the 2009 guidelines (12, 28, 31). Although using 2009 guidelines is preferred because they are more consistent with the widely used WHO BMI categories, researchers should be cautious when retrospectively applying the 2009 guidelines to study cohorts. A recent study found that, compared to 1990 IOM guidelines, 16.7% of women were differentially classified into BMI categories when the 2009 guidelines were used (71). As a result, 17.1% of women classified as adequate gainers under 1990 guidelines were classified as excessive gainers under 2009 guidelines. This issue of differential classification limits the comparability of results from studies using different GWG guidelines. As adoption of the new 2009 guidelines are incorporated into clinical care settings, future studies will more accurately reflect the classification of the study guidelines and improve the comparability of study results.

Racial-ethnic differences in risk factors

Prospective cohort studies are needed to understand the contribution of risk factors by race-ethnicity to GWG or PPWR. Candidate risk factors for racial-ethnic differences in pregnancy-related weight include energy intake and diet quality during pregnancy (24, 68, 72), physical activity during (49, 50) or after pregnancy (33, 73, 74), body image (67), nutrition knowledge (75), clinical advice about recommended GWG (13, 69, 76), length of residency in the US (70), food insecurity (66, 77), postpartum depression (24, 78), social support (79, 80), breastfeeding (16, 24), and sleep duration (17, 21). Ideally, qualitative data will be used to ensure that measurement of exposure data suits the cultural and social context in which women live. The creation of national registries and cohort studies from existing databases such as birth certificates and electronic medical records could allow for inexpensive yet informative studies with sufficient numbers of minorities to allow investigation of maternal and offspring health and offer suggested areas for intervention.

Causal inference

The most pressing gap is the lack of a causal link between maternal GWG and birth outcomes. Though observational studies consistently demonstrate associations, without evidence from randomized trials, we cannot be certain that modifying GWG will improve health outcomes for mothers and babies. Large trials that address excessive GWG and maternal insulin resistance with the goal of affecting fetal and child health (81) are currently in the field; however, we are unaware of any trials aimed at understanding a causal association between inadequate GWG and poor birth outcomes. Furthermore, it is unclear whether the current trials are sufficiently powered to investigate racial-ethnic differences.

Biological plausibility is another line of causal evidence that requires future study. Pregnancy is a unique model for understanding metabolic changes that can lead to chronic diseases. Studies of GWG and PPWR that include detailed biological markers of metabolism and body composition in both mother and offspring are needed to determine the mechanisms and understand metabolic changes that influence fetal growth and maternal obesity such as insulin resistance (82, 83).

Social context

In addition to the individual-based research agenda described above, there is growing evidence that social characteristics beyond the individual are critical to explain variation in these pregnancy and weight-related events. This field is in its infancy and we found only 2 studies that assessed the wider social environment in relation to pregnancy-related outcomes: one that looked at the proximity of supermarkets and diet quality in pregnant women and another that looked at neighborhood factors associated with physical activity and GWG (18, 84). However, a recent study of nonpregnant women reported that whereas black women in the 2008 National Health Interview survey were twice as likely to be obese after adjusting for SES, there was no significant difference in obesity prevalence using data from the Evidence from the Exploring Health Disparities in Integrated Communities-SWB study, a sample of communities where blacks and whites live together with no race differences in SES, based on median income (62). Though these results cannot yet be directly applied to pregnancy-related weight, there is reason to think that targeting obesity reduction at the community level will also address racial-ethnic differences in pregnancy-related weight and birth outcomes.