Prepregnancy BMI
Total weight gain
Rates of weight gain, second and third trimester
Range in kg
Range in lb
Mean (range) in kg/week
Mean (range) in lb/week
Underweight (<18.5 kg/m2)
12.5–18
28–40
0.51 (0.44–0.58)
1 (1–1.3)
Normal weight (18.5–24.9 kg/m2)
11.5–16
25–35
0.42 (0.35–0.50)
1 (0.8–1)
Overweight (25.0–29.9 kg/m2)
7–11.5
15–25
0.28 (0.23–0.33)
0.6 (0.5–0.7)
Obese (≥30 kg/m2)
5–9
11–20
0.22 (0.17–0.27)
0.5 (0.4–0.6)
The 2009 recommendations changed most significantly for women who are overweight or obese prior to pregnancy. These most recent guidelines recommend gains between 15 and 25 lbs for women who are overweight (BMI 25–29.9 kg/m2) and 11 and 20 lbs for women with a BMI in the obese range (BMI 30 kg/m2 or more). Recommendations for teen mothers are not different from those for adult women. It was recommended that short women gain at the lower end of the range. The committee did not have evidence that recommendations should differ based on mother’s race or ethnicity, although they do differ for women with multiple gestation pregnancies [47, 49].
With the release of their recommendations, the IOM suggested strategies to help women adhere to GWG recommendations. Pregnancy is now viewed as a teachable moment, a time in women’s lives when they may be more motivated to make lifestyle and other changes. Helping women achieve an optimal GWG presents an opportunity to impact short- and long-term outcomes for both the mother and her child. If excess GWG plays an independent role in the development of obesity, focused efforts to avoid excess GWG would be warranted. As discussed below, there is little or no experimental evidence to demonstrate that interventions, which effectively limit GWG, improve long-term outcomes for the mother.
Evidence Linking GWG to Outcomes for Overweight and Obese Mothers and Their Babies
Nearly all evidence supporting the link between GWG and outcomes for mothers and their offspring come from observational studies of women across the BMI spectrum. Although these studies consistently demonstrate several important significant associations between GWG and several short- and long-term outcomes [53], they are constrained by failure in most studies to account for the correlation of weight gain with length of pregnancy and increasing fetal weight as a component of weight gain. Maternal obesity is defined as a BMI of 30 kg/m2 or more prior to pregnancy; this group is traditionally further divided into three groups: class I (BMI 30–34.9 kg/m2), class II (35–39.9 kg/m2), and class III (40+ kg/m2). The few studies large enough to focus specifically on obese women suggest that the severity of obesity influences the relation of GWG to outcomes [54, 55]. In this section, we summarize the evidence of a relation for short- and long-term outcomes for women who enter pregnancy overweight or obese.
Short-Term Outcomes
Birth Weight
Observational studies show that inadequate GWG increases the odds of SGA, and moderate evidence shows that excess GWG is linked to LGA [53]. These studies may overestimate the effect because most fail to subtract babies’ weight from total weight gain; the resulting part-whole correlation between the component of weight gain of the fetus and birth weight necessarily overestimates this relation. Kramer and colleagues showed a similar problem when studying preterm birth, which is further compounded by changes in velocity of weight gain over gestation [56]. Recent studies of large cohorts of women, including obese women suggest these associations are stronger for women of normal weight. Among women who are obese, excess GWG is linked to a greater risk of LGA and macrosomia, whereas inadequate weight gain shows a less strong relation with SGA and LBW [57, 58].
Maternal Outcomes
Overweight and obese women are more likely to develop pregnancy complications including gestational diabetes and hypertensive disorders of pregnancy [9]. Results from the EDEN mother-child cohort suggested that net GWG was directly related to the development of gestational hypertension [59]. Findings from investigations exploring the relation of GWG to the development GDM have been mixed [60, 61]. The relation of GWG to other outcomes may be different for women with pregnancy complications, potentially because the diagnosis may prompt lifestyle changes that may affect overall weight gain [51]. For women entering pregnancy obese, interventions during the prenatal and postpartum periods may also mitigate these risks and improve long- and short-term outcomes for mothers and their children. Key targets for intervention include optimizing GWG, encouraging postpartum weight loss, as well as working to address maternal and infant factors that might play a role in setting children’s trajectory towards a healthy weight as they grow.
Prenatal Interventions to Reduce Maternal Weight Gain
Prenatal interventions generally address reduction or restriction in weight gain during pregnancy among samples of pregnant women in general as well as samples of overweight or obese women. The interventions focus primarily on diet, physical activity, and lifestyle alone or in combination. Some studies also evaluated whether additional strategies are needed such as goal setting related to weight loss to enhance the impact of diet and lifestyle interventions. The evidence supporting these interventions is not strong, although it is most consistent for dietary interventions among normal weight women.
Thangaratinam et al. provide the most comprehensive review and meta-analysis of studies of interventions in pregnancy and their impact on maternal weight gain [62, 63]. Their review evaluated 44 randomized controlled trials of interventions related to diet, physical activity, and lifestyle. The results of the meta-analysis show a modest effect of the interventions on reducing weight gain but with considerable heterogeneity across studies. Among the 34 trials evaluating GWG, the impact of any intervention, regardless of the specific intervention, was estimated to result in a reduction of −1.42 kg with 95 % confidence intervals (−0.95; −1.89 kg). The ten trials of dietary interventions alone showed the largest impact with estimates of reduced weight gain of −3.84 kg (−2.45; −5.22 kg) [62]; they also showed the largest effect of all interventions on BMI at delivery, when assessed [63]. The reduction in GWG in the 14 trials of physical activity was modest, −0.72 kg (−1.20; −0.25 kg), as well as in the mixed intervention trials, −1.06 kg (−1.67; −0.46 kg). A small but statistically significant reduction was noted in birth weight in the 28 trials with newborn data. A significantly reduced odds of preeclampsia was shown in 6 trials of dietary interventions and of GDM in 3 trials of dietary interventions. Mixed interventions showed no effect on preeclampsia or GDM, and neither maternal outcome was evaluated in trials of physical activity [62, 63].
The evidence related to weight gain was graded by Thangaratinam et al. as modest, but the overall quality of the evidence for an impact on GDM and gestational hypertension was low [62, 63]. Studies varied by sample characteristics, whether they included overweight or obese women or women of all prepregnancy weight and whether additional components were evaluated such as goal setting. All studies were constrained by selection of women in prenatal care with attendant effects on external validity. Few studies evaluated the impact of the intervention on postpartum weight retention, infant growth, or whether there were real, sustained changes in diet.
The review by Thangaratinam and colleagues included all women regardless of prepregnancy weight [62, 63]. Oteng-Nini et al. reviewed 13 randomized clinical trials and 6 non-randomized studies of prenatal dietary, physical activity, and behavioral and lifestyle interventions among overweight and obese pregnant women [64]. They reported a decrease of −2.21 kg (−2.86; −1.59 kg) in ten trials in which GWG was studied as well as a suggestion of a reduced rate of GDM in studies in which it was evaluated. They found no evidence of a reduction in LGA births. The overall quality of the studies was assessed as low to moderate. The results of a review by Dodd and colleagues also suggested no impact of dietary interventions on LGA births among overweight and obese women [65]. Although they found that women in seven trials gained significantly less weight in the dietary intervention group, adjustment for heterogeneity among studies using random effects models resulted in nonsignificant differences.
Some studies have also evaluated whether interventions may be effective in reducing excessive weight gain during pregnancy [66, 67]. Ronnberg and Nilsson evaluated studies of interventions to reduce excessive GWG and found the evidence to be of insufficient quality to develop recommendations for clinical practice [68]. In an alternative approach, Brown et al. reviewed five studies of goal setting in combination with modifications in diet, physical activity, or both [69]. Although goal setting appeared to be useful to women, the impact of specific aspects of goal setting was unclear.
The results reported by Thangaratinam and colleagues are similar to other reviews conducted on specific interventions [68–72], suggesting some promise for the dietary interventions in particular but limited impact overall of interventions to reduce GWG. There are a number of gaps in the literature, particularly failure to evaluate the long-term impact of the interventions on women or their infants, as noted above. Studies also lack theory or conceptual models to support the interventions from a behavioral modification perspective [70], although some attention was given to goal-setting strategies as a component of the intervention [69]. There is also limited information about specific interventions, making it difficult to replicate studies or to develop clinical practice recommendations. Studies are needed with adequate samples to evaluate the reasons for heterogeneity of findings across studies and to evaluate whether there are subgroups of women who would benefit most from specific interventions. In addition, it is reasonable to postulate that dietary interventions which result in close to a 4 kg reduction in weight gain may also reduce postpartum weight retention, but the magnitude of the impact may be small over the life course of a woman if the intervention does not result in long-term change in diet or alter whether or not a woman becomes overweight or obese.
Maternal Prepregnancy BMI Associated with Decreased Initiation and Shorter Duration of Breastfeeding
High prepregnancy BMI can adversely effect breastfeeding rates. Despite Healthy People 2020 Goals [73], recommendations of the American Academy of Pediatrics [74], and widespread recognition of the benefits of breastfeeding, the percentage of women who breastfeed in the United States did not meet the Healthy People 2010 goals. Among all births in the United States in 2006, 74 % of mothers ever breastfed and 44 % continued through 6 months of age. The corresponding the American Academy of Pediatrics similarly recommends exclusive breastfeeding through 6 months of age and continued breastfeeding for 1 year or longer as complementary foods are introduced and as mutually desired by mother and infant [74].
In a review of the literature, Wojicki reported 12 studies of breastfeeding initiation; the results of 9 studies showed an association between overweight and obesity prior to pregnancy and failure to initiate breastfeeding [75]. Of the 12 studies that considered duration, 10 reported an association between maternal overweight or obesity and decreased duration. Among 2 of the 9 studies of breastfeeding initiation and 2 of the 10 focusing on duration, these relations were observed for selected subgroups, although most studies did not stratify analyses by race and ethnicity. Wojicki suggests that differences by race and ethnicity may reflect underlying sociocultural, environmental, or physiological factors and that these factors are important to address in interventions to promote breastfeeding.
Most studies of breastfeeding have not considered the role of medical complications. Kistantis et al. conducted a study that stratified analyses by presence or absence of medical and delivery complications (e.g., hypertension, fetal distress, gestational diabetes, meconium) [76]. The study results showed that decreased initiation and duration was limited to overweight or obese women with complications. Wojicki noted that possible reasons underlying the association between obesity and breastfeeding may relate to biological changes (delayed prolactin response), mechanical issues (positioning the infant), behavioral factors (choice and intentions), and psychological factors [75].
In a Belgian retrospective cohort study of 200 women, Guelinckx et al. reported decreased initiation and duration of breastfeeding among both obese and underweight women with no association between initiation and hypertensive disorders [77]. More recently, in a sample of 550 women participating in the Pregnancy, Infection, and Nutrition Postpartum Study, Mehta and colleagues confirmed the link between prepregnancy overweight and obesity and reduced initiation and duration of breastfeeding [78]. Most importantly, they found that these relations were not mediated by depressive symptoms, perceived stress, or anxiety during pregnancy.
Although the association between obesity and decreased initiation and breastfeeding well established in the literature, there is little understanding of the underlying mechanisms. While primary efforts are needed to reduce obesity, further studies also are needed to understand the underlying mechanisms in order to determine whether interventions should address mutable factors that may increase breastfeeding among obese women. These factors may include anatomic barriers that require support of breasts to facilitate appropriate latch-on, reduced willingness to seek support for breastfeeding that requires enhanced and targeted outreach, and concerns over body image which might necessitate strategies to promote comfort of breastfeeding in public [77]. In the absence of studies, it is difficult to understand the barriers to breastfeeding among obese women.
Maternal Prepregnancy BMI and Gestational Weight Gain Influence Infant Growth at 1 Year
In addition, to birth outcomes discussed previously, prepregnancy weight also is associated with infant postnatal growth. Growth in the first year of life is of particular interest given the association between rapid early growth and subsequent childhood obesity [79–81] and cardiovascular disease and diabetes in adulthood [82, 83]. In addition, growth in the first year of life reflects the establishment of early feeding, physical activity, and sleep practices which, when unfavorable, may contribute to the development of obesity in later childhood. Numerous studies have also determined early growth rate to be a strong predictor of childhood obesity [84].
Using data from the Pregnancy, Infection, and Nutrition Study, Deierlein et al. reported that prepregnancy overweight and obesity were associated with greater weight for age and weight for length at 6 months, but not with length for age, after accounting for other infant and maternal characteristics [85]. The relations were attenuated, however, when birth weight was taken into account in the analysis, the effect of prepregnancy overweight and obesity on growth indices at 6 months were largely explained by the relation of prepregnancy weight with prenatal growth.
With regard to body composition, Chandler-Laney et al. observed that prepregnancy BMI was also associated with a child’s total lean mass, but not total fat mass or trunk fat mass at 12 months, after adjusting for infant length and rate of weight gain in the first year [86]. The authors speculate that the association may be attributed to genetic susceptibility or the intrauterine environment. Total and trunk fat mass, in their study, was associated with weight gain in the first year of life, particularly in the first 6 months; this association is of particular interest given the role of rapid weight gain in early infancy on future body composition and fat deposition.
Data from the Pregnancy, Infection, and Nutrition Study also inform our understanding of the relation of GWG to infant growth [87]. Infants born to women with GWG up to 199 % of the 2009 Institute of Medicine (IOM) recommendations had higher weight for age and length for age z-scores between birth and 3 years of age than women with appropriate GWG, while infants born to women with GWG of 200 % or more of the recommendations experienced higher weight for age, length for age, and weight for length z-scores. These findings were first observed in early infancy and persisted through 3 years of age. Also, these associations remained after adjusting for prepregnancy BMI, maternal diabetes prior to pregnancy, and demographic characteristics. The authors note that “in utero programming effects beyond fetal growth” may contribute to persistent faster rates of growth as might the postnatal feeding environment (e.g., feeding behaviors, diet quality) and genetic susceptibility to rapid growth.
Multiple studies suggest that increased GWG in pregnancy is associated with higher growth parameters in the first year of life, through adolescence and into adulthood. The extent to which the accompanying adiposity, hypertension, and lipid abnormalities that track into adulthood are related to subsequent obesity, in utero exposures, or genetic susceptibility remains unclear. Moreover, the association of GWG with childhood BMI and adiposity likely varies by prepregnancy BMI status with inconsistent results reported, although generally stronger relations are found among women who are under or normal weight [13, 88]. Gillman argues that prepregnancy BMI, rather than GWG, is a more relevant, modifiable factor and suggests further need to understand the different components of weight gain during pregnancy including maternal tissue, fluid accumulation, the placenta, and the fetus [89]. Chandler-Laney explored the role of GWG in predicting lean mass at 12 months and found no association independent of prepregnancy BMI [86], while others, as reviewed by Poston, have reported associations between GWG and greater fat mass later in childhood and adulthood [90].
Further work is needed to understand the independent effects of prepregnancy BMI and GWG on infant growth and body composition in order to design more effective interventions [91]. A two pronged approach of optimizing the health of women prior to pregnancy and assuring appropriate weight gain during pregnancy may be needed to improve pregnancy outcomes and assure that infants start life on a healthy trajectory with regard to nutritional and metabolic status.
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