
==== Front
Am J Clin Nutr
Am J Clin Nutr
The American Journal of Clinical Nutrition
0002-9165
1938-3207
American Society for Nutrition

S0002-9165(24)00583-5
10.1016/j.ajcnut.2024.06.011
Original Research Article
Gestational weight gain below recommendations and adverse maternal and child health outcomes for pregnancies with overweight or obesity: a United States cohort study
Bodnar Lisa M lbodnar@pitt.edu
123⁎
Johansson Kari 45
Himes Katherine P 6
Khodyakov Dmitry 7
Abrams Barbara 8
Parisi Sara M 1
Hutcheon Jennifer A 9
1 Department of Epidemiology, School of Public Health, University of Pittsburgh, Pittsburgh, PA, United States
2 Department of Obstetrics, Gynecology, and Reproductive Sciences, School of Medicine, University of Pittsburgh, Pittsburgh, PA, United States
3 Magee-Womens Research Institute, Pittsburgh, PA, United States
4 Clinical Epidemiology Division, Department of Medicine Solna, Karolinska Institutet, Stockholm, Sweden
5 Department of Women’s Health, Karolinska University Hospital, Stockholm, Sweden
6 Department of Obstetrics and Gynecology, Dartmouth Hitchcock Medical Center, Hanover, NH, United States
7 RAND Health Care, Santa Monica, CA, United States
8 Division of Epidemiology, School of Public Health, University of California, Berkeley, Berkeley, CA, United States
9 Department of Obstetrics and Gynecology, University of British Columbia, Vancouver, Canada
⁎ Corresponding author. lbodnar@pitt.edu
26 6 2024
9 2024
26 6 2024
120 3 638647
2 4 2024
3 6 2024
24 6 2024
© 2024 The Author(s)
2024
https://creativecommons.org/licenses/by-nc-nd/4.0/ This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/4.0/).
Background

The current Institute of Medicine (IOM) pregnancy weight gain guidelines were developed using the best available evidence but were limited by substantial knowledge gaps. Some have raised concern that the guidelines for individuals affected by overweight or obesity are too high and contribute to short- and long-term complications for the mother and child.

Objectives

To determine the association between pregnancy weight gain below the lower limit of the current IOM recommendations and risk of 10 adverse maternal and child health outcomes among individuals with overweight and obesity.

Methods

We used data from a prospective cohort study of United States nulliparae with prepregnancy overweight (n = 955) or obesity (n = 897) followed from the first trimester to 2–7 y postpartum. We used multivariable Poisson regression to relate pregnancy weight gain z-scores with a severity-weighted composite outcome consisting of ≥1 of 10 adverse outcomes (gestational diabetes, preeclampsia, unplanned cesarean delivery, maternal postpartum weight increase >10 kg, maternal postpartum metabolic syndrome, infant death, stillbirth, preterm birth, small-for-gestational age birth, and childhood obesity).

Results

Pregnancy weight gain z-scores below, within, and above the IOM-recommended ranges occurred in 5%, 13%, and 80% of pregnancies with overweight and 17%, 13%, and 70% of pregnancies with obesity. There was a positive association between pregnancy weight gain z-scores and all adverse maternal outcomes, childhood obesity, and the composite outcome. Pregnancy weight gain z-scores below the lower limit of the recommended ranges (<6.8 kg for overweight, <5 kg for obesity) were not associated with the severity-weighted composite outcome. For example, compared with the lower limit, adjusted rate ratios (95% confidence interval) for z-scores of −2 standard deviations in pregnancies with overweight (equivalent to 3.6 kg at 40 wk) and obesity (−2.8 kg at 40 wk) were 0.99 (95% confidence interval [CI]: 0.91, 1.06) and 0.97 (95% CI: 0.87, 1.07).

Conclusions

These findings support arguments to decrease the lower limit of recommended weight gain ranges in these prepregnancy body mass index groups.

Keywords

cohort study
epidemiology
nutrition
perinatal
public health recommendations
obstetrics
Abbreviations

CI confidence interval

IOM Institute of Medicine

nuMoM2b Nulliparous Pregnancy Outcomes Study: monitoring mothers-to-be

nuMoM2b-HHS Nulliparous Pregnancy Outcomes Study: monitoring mothers-to-be Heart Health Study

RR rate ratio

SGA small-for-gestational-age
==== Body
pmcIntroduction

Half of the pregnant individuals in the United States start pregnancy affected by overweight or obesity, and in some states, the estimates reach nearly 60% [1]. As prepregnancy BMI rises, the risks of a myriad of short- and long-term health outcomes increase, including preeclampsia, gestational diabetes, and future cardiovascular disease risk for the mother, as well as perinatal death, preterm birth, obesity, and neurocognitive disorders for the child [[2], [3], [4], [5], [6]]. Pregnant individuals with overweight or obesity and their children have higher health care utilization and costs ≤18 y after delivery compared with pregnant individuals with normal weight [7,8]. The American College of Obstetricians and Gynecologists recommends optimizing weight gain during pregnancy to reduce the burden of maternal overweight and obesity [9]. They endorse the use of the Institute of Medicine’s (IOM) ’s 2009 guidelines for weight gain during pregnancy, including total weight gains at term of 6.8‒11.3 kg and 5.0–9.1 kg for individuals with prepregnancy overweight and obesity, respectively [10]. These guidelines aimed to balance risk associated with high and low weight gain to reduce the overall risk.

The IOM developed its guidelines using the best available evidence, but recognized that the final recommendations were limited by substantial knowledge gaps. High-quality evidence on the optimal pregnancy weight gain needed to prevent highly relevant adverse health outcomes, including preeclampsia, gestational diabetes, long-term maternal obesity and cardiometabolic disease, and childhood obesity were unavailable [10]. Furthermore, data on the safety of low weight gain or weight loss were generally limited to evaluations of small-for-gestational-age (SGA) birth risk. Finally, the guidelines did not account for the need to balance risk of the multitude of adverse outcomes associated with high and low weight gain for both the pregnant individual and child.

Since 2009, scientists and health care providers have raised concerns that the guidelines for individuals affected by overweight or obesity are too high and contribute to pregnancy complications and the intergenerational cycle of obesity [9,[11], [12], [13]]. Randomized trials to restrict pregnancy weight gain in high BMI groups [[14], [15], [16], [17], [18]] showed potential benefits and no known serious risks. The studies, however, had small samples and short follow-up, which limited inferences that could be drawn regarding the safety of low weight gain. We sought to build on this literature by determining the association between weight gain below the lower limit of current pregnancy weight gain recommendations and risks of 10 short- and long-term adverse maternal and child health outcomes in a geographically, racially, and socioeconomically diverse United States cohort of pregnancies with overweight and obesity.

Methods

The Nulliparous Pregnancy Outcomes Study: monitoring mothers-to-be (nuMoM2b) was a pregnancy cohort study at 8 medical centers in the United States from October 2010 to September 2013 (ClinicalTrials.gov NCT01322529) [19]. Participants were eligible if they were 6‒13 wk gestation with a singleton pregnancy and had no prior pregnancy lasting ≥20 wk gestation. At enrollment in the first trimester, study personnel conducted interviews to collect data on demographics, medical history, location of residence, behaviors, and psychosocial factors. At least 30 d after delivery, a trained certified chart abstractor recorded final birth outcomes, delivery diagnoses, and pregnancy complications.

The nuMoM2b Heart Health Study (nuMoM2b-HHS) was a postpartum follow-up of this cohort (September 2014‒October 2020) with interval contacts by phone every 6 mo and 1 in-person study visit 2–7 y after delivery [mean 3.2 y; standard deviation (SD): 0.9] (ClinicalTrials.gov NCT02231398) [20]. Blood pressure and body measurements were recorded at the in-person visit, fasting blood was drawn, and sociodemographic data were collected. Human subjects review boards approved the studies, and all participants provided informed, written consent in their native language.

Of the 8838 nuMoM2b participants eligible for nuMoM2b-HHS, 7003 were contacted to participate, and 4518 completed an in-person study visit at 2‒7 y postpartum. Characteristics of individuals in the follow-up study were similar to the full nuMoM2b cohort [21]. For our analysis, we included participants who were not currently pregnant or within 6 mo postpartum of another pregnancy, who did not have pre-existing diabetes before the index pregnancy (as they were not at risk of developing gestational diabetes, one of the outcomes of interest), or whose prepregnancy BMI was missing. We focused on participants with prepregnancy overweight or obesity in the index pregnancy, and therefore excluded individuals with a BMI < 25 kg/m2. Our research in individuals with normal weight has been previously published [22].

Pregnancy weight gain

At the first nuMoM2b study visit, study personnel measured participants’ height, and they self reported their weight. Prepregnancy BMI was calculated as weight (kg) divided by height (m) squared. BMI 25‒29.9 kg/m2 and ≥30 kg/m2 defined overweight and obesity, respectively.

We calculated pregnancy weight gain as the last measured weight before delivery minus self-reported prepregnancy weight (kg). If delivery weight was not available, we used the last measured weight ≤4 wk before delivery. The median (interquartile range) time between last measured weight and delivery was 1 (3) days. For individuals who had preeclampsia or gestational diabetes, we used the last weight measured before their diagnosis (16‒20 wk) rather than the last week at delivery, because these complications themselves can alter pregnancy weight gain [10]. Using a measured weight before diagnosis avoids problems of reverse causality [23]. We converted total pregnancy weight gain into gestational age-specific z-scores using BMI-specific charts from a Pennsylvania population [24] (Supplemental Table 1). Our approach to identify and account for implausible height, weight, and weight gain values is described in the Supplemental Methods.

Composite outcome

We created a composite outcome that consisted of one or more of 10 short- and long-term maternal and child health outcomes described below. We selected these outcomes because they have been consistently associated with pregnancy weight gain, as illustrated in the 2009 IOM scientific report [10], systematic reviews, and other recent literature [[25], [26], [27], [28], [29], [30], [31], [32], [33], [34], [35], [36], [37], [38], [39]], and are feasible to operationalize or measure in large research studies [40].

The outcomes were gestational diabetes [41,42], preeclampsia [43], unplanned cesarean delivery, >10 kg postpartum weight change between prepregnancy weight at the index pregnancy and measured weight at 2–7 y postpartum, postpartum metabolic syndrome [21,44], preterm birth [19], SGA birth [45], stillbirth, neonatal death, and childhood obesity at 2–5 y [46] (definitions in Supplemental Methods). As a secondary composite outcome, we replaced a >10 kg postpartum weight increase with >5 kg postpartum weight increase.

Accounting for outcome seriousness

The 10 health outcomes in our composite differ in their relative seriousness [47]. We, therefore, weighted each outcome using seriousness scores that we previously elicited from a geographically and racially diverse group of 166 United States health professionals and pregnant and postpartum individuals through an online modified Delphi process [40,47]. Scores ranged from 0 (not at all serious) to 100 (the most serious). We used the median score to weigh each outcome in the composite: infant death, 100; stillbirth, 95; preterm birth, 80; preeclampsia, 80; childhood obesity, 65; >10 kg weight increase postpartum (as a proxy for longer-term obesity in birthing individuals), 60; postpartum metabolic syndrome, 60; gestational diabetes, 55; SGA birth, 40; unplanned cesarean delivery, 30 [47]. When maternal–child dyads had more than one adverse outcome, we summed seriousness scores for the final severity-weighted composite outcome.

Confounders

A description of our rationale for confounder selection, methods of data collection, and detailed definitions have been published previously [48] and are summarized in the Supplemental Methods. Confounders had a potential causal relationship with pregnancy weight gain and the outcomes of interest and were not downstream from weight gain [49]. Confounders were measured in the first trimester and included sociodemographic factors (participant’s age, education, race and ethnicity (as proxies for exposure to structural racism), marital status, and medical insurance), medical factors (chronic hypertension, nausea and vomiting [50], and prepregnancy BMI), behavioral factors (prepregnancy smoking, binge drinking, preconception diet quality as measured by the Healthy Eating Index–2015 total score [51], preconception physical activity [52], and sleep satisfaction [53]), psychosocial factors (depressive symptoms [54], and anxiety [55]), and neighborhood factors (neighborhood poverty, proximity to grocery stores, walkability [56], resilience [57], and deprivation [58]).

Statistical analysis

To provide a visual representation of dietary pattern [59], we created radar plots by weight gain category for individuals with overweight and obesity, with each HEI–2015 component score depicted as a mean of the percentage of maximum points on its respective axis.

We associated pregnancy weight gain z-scores to each individual health outcome and to our composite outcome using BMI-stratified Poisson regression with robust standard errors [60]. We chose the referent value in all models to be the pregnancy weight gain z-score that corresponded to the lower limit of the IOM recommendations for individuals affected by overweight (z-score −1.4 SD corresponding to 6.8 kg at 40 wk) or obesity (z-score −0.8 SD, 5 kg at 40 wk). We calculated the incident rate ratios (RRs) and 95% confidence intervals (CIs) for each 0.1 SD increment in weight gain z-score from −3.0 to 3.0 SD compared with the lower limit of the IOM-recommended ranges. This approach allowed us to determine whether the rate of the severity-weighted composite outcome across the weight gain distribution was meaningfully different from the rate for weight gain below the recommendations.

We first modeled the composite outcome in which all outcomes were weighted equally (“unweighted”). Then, we modeled the composite after weighting each health outcome in the composite according to the abovementioned seriousness scores. In these severity-weighted models, the total score assigned to each mother–child dyad was modeled as the outcome [61]. Pregnancy weight gain z-score was converted to a restricted cubic spline with 3 knots in the default positions to allow smooth, nonlinear relationships [62]. We adjusted for confounders, centered to their mean value. Confounders included participant’s age (years continuous), education (High school or less, some college, college graduate, graduate degree), race/ethnicity (non-Hispanic White, non-Hispanic Black, Hispanic, other), marital status (married, not married), prepregnancy smoking (yes, no), gravidity (0, 1, or more), medical insurance (private, public or other), chronic hypertension (yes/no), diet quality (continuous Healthy Eating Index-2015 score), physical activity (<450, 450–899, ≥900 metabolic equivalent task (MET) minutes/week), nausea and vomiting (mild, moderate, or severe), binge drinking (yes, no), sleep satisfaction (restless or average, restful or very restful), depressive symptoms (low, high), anxiety (low, high), resilience (Connor–Davidson Resilience Scale, continuous), neighborhood walkability (National Walkability Index, continuous), neighborhood deprivation (Area Deprivation Index, continuous), proximity to grocery stores (km, categorized into thirds based on tertiles), and percentage of neighborhood with income below the poverty line (continuous).

Missing outcome or exposure data were addressed using multiple imputation. CIs were calculated through bootstrapping, using 10,000 bootstrapped samples [63,64].

In a secondary analysis, we replaced postpartum weight increase >10 kg in the composite with an increase of >5 kg (using the same seriousness weight for this outcome).

Stata version 17 (StataCorp) was used for analyses. We presented RRs and 95% CIs, to avoid misleading significance threshold interpretations commonly associated with P values [65,66].

Results

From the cohort of participants who attended the in-person postpartum study visit (n = 4518), we excluded participants who had pregestational diabetes (n = 62) or whose index pregnancy ended at <20 wk (n = 22), were pregnant or <6 mo postpartum at the postpartum study visit (n = 73), or had missing data on prepregnancy BMI (n = 6) (Supplemental Figure 1). Our analysis focused on participants with prepregnancy overweight or obesity, and therefore we excluded participants affected by underweight (n = 159) or normal weight (n = 2344). The final analytic sample was 955 participants with overweight and 897 with obesity.

Over half of the cohort was non-Hispanic White, college-educated, married, nonsmokers, and had private medical insurance (Table 1 [50,51,54,55]). Pregnant participants with obesity were more likely than those with overweight to be non-Hispanic Black, unmarried, and smokers, and to have chronic hypertension, a sedentary lifestyle, and a high school or less education. There were no notable differences in diet quality, nausea and vomiting, sleep satisfaction, or depressive symptoms. Of the participants with obesity, 52% (n = 467), 27% (n = 242), and 21% (n = 188) had class 1, class 2, and class 3 obesity, respectively.TABLE 1 Characteristics of pregnancies with overweight or obesity, Nulliparous Pregnancy Outcomes Study: monitoring mothers-to-be Heart Health Study.

TABLE 1	Overweight n = 9551	Obese n = 897	
	n (%) or mean (SD)	
Maternal age, y	27 (5.7)	26 (5.6)	
Maternal race/ethnicity	
 Non-Hispanic White	571 (60)	456 (51)	
 Non-Hispanic Black	146 (15)	227 (25)	
 Hispanic	184 (19)	155 (17)	
 Other	54 (6)	59 (7)	
Maternal education	
 High school or less	200 (21)	231 (26)	
 Some college	318 (33)	351 (39)	
 College graduate	255 (27)	200 (22)	
 Graduate degree	182 (19)	115 (13)	
Marital status	
 Not married	392 (41)	468 (52)	
 Married	563 (59)	429 (48)	
Insurance at delivery	
 Private	631 (66)	540 (60)	
 Public or self-pay	324 (34)	357 (40)	
Chronic hypertension	
 No	927 (97)	807 (90)	
 Yes	28 (3)	90 (10)	
Preconception smoking status	
 Nonsmoker	791 (83)	693 (77)	
 Smoker	162 (17)	203 (23)	
 Missing	2 (0.2)	1 (0.1)	
 Periconception Healthy Eating Index – 2015 total score	64 (11)	61 (11)	
First-trimester physical activity	
 Inactive (0 MET2 min/wk)	309 (32)	357 (40)	
 Low activity (1–499 MET min/wk)	259 (27)	255 (28)	
 Active (500–1000 MET min/wk)	166 (17)	142 (16)	
 Highly active (>1000 MET min/wk)	217 (23)	143 (16)	
 Missing	4 (0.4)	0	
Severity of nausea and vomiting in early pregnancy	
 Mild	783 (82)	726 (81)	
 Moderate or severe	172 (18)	171 (19)	
First-trimester sleep satisfaction	
 Restless	187 (20)	187 (21)	
 Average	345 (36)	333 (37)	
 Restful or very restful	296 (31)	251 (28)	
 Missing	127 (13)	126 (14)	
First-trimester depressive symptoms	
 Low	790 (83)	738 (82)	
 High	141 (15)	133 (15)	
 Missing	24 (2)	26 (3)	
First-trimester anxiety	
 Low	628 (66)	542 (60)	
 Moderate or high	209 (22)	235 (26)	
 Missing	118 (12)	120 (13)	
 Percent of neighborhood in poverty	18 (13)	20 (14)	
Abbreviations: MET, metabolic equivalent task; SD, standard deviation.

References for standardized tools are: Healthy Eating Index – 2015 [51], Pregnancy-Unique Quantification of Emesis and Nausea (PUQE) index [50], Edinburgh Postnatal Depression Scale[54], State-Trait Anxiety Inventory [55].

1 Missing data for maternal age, n = 0 for overweight and n = 0 for obese; Healthy Eating Index total score, n = 162 for overweight and n = 153 for obese; percentage of neighborhood in poverty, n = 31 for overweight and n = 35 for obese.

The total pregnancy weight gains for participants with overweight and obesity were 15.5 kg (z-score 0.08 SD) and 11.2 kg (z-score 0.05 SD), respectively. ∼13% of individuals in either BMI group gained within the IOM-recommended range; gaining below or above the guidelines occurred in 5% (n = 58) and 80% (n = 765) of pregnancies with overweight and 17% (n = 153) and 70% (n = 624) of pregnancies with obesity. Only 0.6% (n = 6) of participants with overweight gained no weight or lost weight; this increased to 6.5% (n = 57) in individuals affected by obesity.

Among individuals whose weight gain z-score indicated that they gained below, within, and above the IOM guidelines, 32%, 35%, and 42% of those affected by overweight and 30%, 25%, and 35% of those affected by obesity met the national physical activity recommendations in the first trimester. Across these weight gain groups, the mean (95% CI) total HEI–2015 score did not meaningfully vary [overweight: 60 (95% CI: 57, 63), 61 (95% CI: 59, 63), 64 (95% CI: 64, 65); obesity: 58 (95% CI: 56, 60), 60 (95% CI: 58, 62), 62 (95% CI: 61, 64)]. There were only small differences in HEI–2015 component scores comparing individuals with overweight who gained below and within the guidelines (Supplemental Figure 2). Participants who gained less than the IOM guidelines were somewhat less likely than those who gained within the guidelines to meet recommendations for Total Vegetables, Greens and Beans, and Added Sugars, and more likely to meet the guidelines for Refined Grains and Saturated Fats. No meaningful differences were observed in intakes of Total Fruit, Whole Fruits, Whole Grains, Dairy, Total Protein Foods, Seafood and Plant Proteins, Fatty Acids, or Sodium. For individuals with obesity, dietary patterns did not differ by pregnancy weight gain (Supplemental Figure 3).

The most common adverse outcomes experienced by participants were unplanned cesarean delivery, >10 kg postpartum weight increase, and postpartum metabolic syndrome (21%–38%). Gestational diabetes, preeclampsia, preterm birth, SGA birth, and child obesity occurred in 6%–17% (Table 2). Of these 8 outcomes, all except SGA birth were more common in pregnancies with obesity than with overweight. Only 3 pregnancies had a stillbirth or neonatal death. ∼70% and 82% of participants affected by overweight and obesity had at least one of these adverse outcomes.TABLE 2 Unadjusted incidence of adverse maternal and child health conditions according to gestational weight gain z-scores indicating weight gain below, within, or above the 2009 Institute of Medicine recommendations among pregnancies with overweight and obesity in the Nulliparous Pregnancy Outcomes Study: monitoring mothers-to-be Heart Health Study.

TABLE 2	Prepregnancy overweight	Prepregnancy obesity	
Overall, n = 955	Pregnancy weight gain z-score	Overall, n = 897	Pregnancy weight gain z-score	
<−1.41	−1.4 to 0.6	>−0.62	<−0.751	−0.75 to 0.25	>−0.252	
Equivalent total pregnancy weight gain at 40 wk, kg	Equivalent total pregnancy weight gain at 40 wk, kg	
<6.8 kg, n = 58	6.8 to 11.4 kg, n = 132	>11.4 kg, n = 765	<5 kg, n = 153	5 to 9.1 kg, n = 120	>9.1 kg, n = 624	
Health condition	Cases, n (%)	Cases, n (%)	
Gestational diabetes	57 (6.0)	4 (6.8)	6 (4.7)	47 (6.1)	90 (10)	16 (12)	10 (8.2)	62 (9.9)	
Preeclampsia	89 (9.3)	6 (9.6)	13 (9.4)	71 (9.3)	141 (16)	19 (14)	16 (13)	105 (17)	
Unplanned cesarean	225 (24)	10 (18)	26 (20)	188 (25)	293 (33)	34 (25)	48 (40)	207 (33)	
>10 kg Postpartum weight increase	305 (32)	12 (21)	20 (15)	273 (36)	323 (36)	29 (21)	36 (30)	256 (41)	
Postpartum metabolic syndrome	203 (21)	15 (26)	29 (22)	159 (21)	342 (38)	53 (38)	48 (40)	237 (38)	
Preterm birth <37 wk	87 (9.1)	8 (14)	17 (12)	63 (8.2)	90 (10)	15 (11)	9 (7.8)	65 (10)	
Small-for-gestational-age birth	68 (7.1)	10 (16)	14 (10)	44 (5.8)	82 (9.2)	20 (15)	12 (10)	46 (7.3)	
Stillbirth	3 (3.1)	0	1 (0.8)	2 (0.3)	2 (2.2)	1 (0.74)	0	1 (0.1)	
Neonatal death	1 (1.0)	0	0	1 (0.1)	2 (2.2)	0	0	2 (0.3)	
Childhood obesity	118 (12)	6 (10)	14 (10)	98 (13)	156 (17)	24 (17)	24 (20)	108 (17)	
Any adverse outcome	668 (70)	40 (69)	82 (65)	542 (71)	735 (82)	105 (77)	101 (84)	519 (83)	
1 Cutoff corresponds to the lower limit of the current 2009 IOM recommendations.

2 Cutoff corresponds to the upper limit of the current 2009 IOM recommendations.

Pregnancy weight gain association with individual health outcomes

Among participants in both BMI groups who gained greater than the IOM guidelines, unplanned cesarean delivery, postpartum weight increase, and any adverse outcome were higher, and preterm birth and SGA birth were lower compared with those who gained less weight than the guidelines (Table 2). Incidence of other outcomes varied across weight gain categories. After adjustment for confounders, relationships between adverse outcomes and pregnancy weight gain in participants with overweight were generally positive for postpartum weight increase, unplanned cesarean delivery, preeclampsia, and childhood obesity, negative for SGA birth, and U-shaped for metabolic syndrome, preterm birth, and gestational diabetes (Figure 1; Supplemental Tables 2‒7). The only differences for individuals with obesity were unplanned cesarean delivery (reverse U-shaped) and gestational diabetes (positive).FIGURE 1 Confounder-adjusted association between pregnancy weight gain z-score and adverse maternal and child health conditions among pregnancies with overweight (A, n = 955) or obesity (B, n = 897) in the Nulliparous Pregnancy Outcomes Study: monitoring mothers-to-be Heart Health Study. Predicted rates of each adverse health outcome for the pregnant individual and child have been adjusted for participant’s age, education, race/ethnicity, marital status, prepregnancy smoking, gravidity, medical insurance, chronic hypertension, diet quality, physical activity, nausea and vomiting, binge drinking, sleep satisfaction, depressive symptoms, anxiety, neighborhood walkability, neighborhood deprivation, proximity to grocery stores, and percent of neighborhood with income below the poverty line. Stillbirth and neonatal death have been omitted due to small numbers of cases. For gestational diabetes and preeclampsia cases, the total weight gain before diagnosis was used to calculate pregnancy weight gain z-scores. The upper x-axis refers to the total pregnancy weight gain (kg) that is equivalent to pregnancy weight gain z-scores at 40 wk.

FIGURE 1

For both BMI groups, the adverse outcome most strongly associated with pregnancy weight gain was postpartum weight increase. For example, participants with a pregnancy weight gain z-score of −1 (equivalent to a 40-wk weight gain of 9 kg for overweight and 3.2 kg for obese) had 13% and 21% risks of postpartum weight increase >10 kg; among those with a pregnancy weight gain z-score of +1 (equivalent to a 40-wk weight gain of 25 kg for overweight and 23 kg for obese), these risks were 41% for both BMI groups. For a >5 kg increase in postpartum weight, this change in prevalence was 29%–65% for overweight and 41%–64% for obesity.

Pregnancy weight gain association with the composite outcome

The adjusted RRs for the severity-weighted composite adverse outcome according to pregnancy weight gain z-score are shown in Figure 2, with numeric values provided in Supplemental Tables 8 and 9. Lower limits of the IOM-recommended weight gain ranges (z-score -1.4 SD corresponding to 6.8 kg at 40 wk for overweight and −0.8 SD and 5 kg for obese) were the referent values. In both BMI categories, weight gain z-scores below the lower limits of the IOM-recommended ranges were not associated with meaningfully increased RRs. For example, compared with the lower limit of each BMI group’s guidelines, the adjusted RR (95% CI) for z-scores of −2 SD in overweight pregnancies (corresponding to 3.6 kg at 40 wk) and in pregnancies with obesity (−2.8 kg at 40 wk) were 0.99 (95% CI: 0.91, 1.06) and 0.97 (95% CI: 0.87, 1.07), respectively. For pregnancies with obesity, this null association included all weight gain z-scores at which no weight gain or weight loss occurred (z-scores <−1.5 SD).FIGURE 2 Confounder-adjusted associations between pregnancy weight gain z-score and a severity-weighted composite of adverse maternal and child health outcomes compared with the lower limit of the Institute of Medicine (IOM) recommended ranges. Pregnancies with overweight (A, n = 955) and obesity (B, n = 879), Nulliparous Pregnancy Outcomes Study: monitoring mothers-to-be Heart Health Study. The association between pregnancy weight gain z-score and the severity-weighted composite outcome. Outcomes included in the composite are gestational diabetes, preeclampsia, unplanned cesarean delivery, postpartum weight change >10 kg, postpartum metabolic syndrome, stillbirth, infant death, preterm birth, small-for-gestational-age birth, and childhood obesity. The circles represent the adjusted RRs and lines represent the 95% confidence intervals. The light blue circles indicate the estimates associated with no weight gain or weight loss. The vertical gray dotted line indicates the cutpoints for the 2009 IOM pregnancy weight gain recommendations. The referent is the z-score that is equivalent to the lower limit of the recommendations (−1.4 for overweight and -0.8 for obese). The upper x-axis refers to the total pregnancy weight gain (kg) that is equivalent to pregnancy weight gain z-scores at 40 wk. Severity-weighted RRs (95% confidence intervals) have been adjusted for participant’s age, education, race/ethnicity, marital status, prepregnancy smoking, gravidity, medical insurance, chronic hypertension, diet quality, physical activity, nausea and vomiting, binge drinking, sleep satisfaction, depressive symptoms, anxiety, neighborhood walkability, neighborhood deprivation, proximity to grocery stores, and percentage of the neighborhood with income below the poverty line. For gestational diabetes and preeclampsia cases, the total weight gain before diagnosis was used to calculate pregnancy weight gain z-scores. CI, confidence interval.

FIGURE 2

When we replaced postpartum weight increase >10 kg in the severity-weighted composite with >5 kg increase, conclusions were similar (Figure 3; Supplemental Tables 10 and 11). There were no meaningful differences in weight gain values below IOM recommendations in the association between pregnancy weight gain and the composite outcome when the 10 health conditions were given equal weight compared with when they are severity-weighted (Supplemental Figure 4).FIGURE 3 Confounder-adjusted associations between pregnancy weight gain z-score and a severity-weighted composite of adverse maternal and child health outcomes (replacing >10 kg postpartum weight increase with >5 kg increase) compared with the lower limit of the Institute of Medicine (IOM) recommended ranges. Pregnancies with overweight (A, n = 955) and obesity (B, n = 897), Nulliparous Pregnancy Outcomes Study: monitoring mothers-to-be Heart Health Study. The association between pregnancy weight gain z-score and the severity-weighted composite outcome. Outcomes included in the composite are gestational diabetes, preeclampsia, unplanned cesarean delivery, postpartum weight change >5 kg, postpartum metabolic syndrome, stillbirth, infant death, preterm birth, small-for-gestational-age birth, and childhood obesity. The circles represent the adjusted RRs and lines represent the 95% confidence intervals. The light green circles indicate the estimates associated with no weight gain or weight loss. The vertical gray dotted line indicates the cutpoints for the 2009 IOM pregnancy weight gain recommendations. The referent is the z-score that is equivalent to the lower limit of the recommendations (−1.4 for overweight and −0.8 for obese). The upper x-axis refers to the total pregnancy weight gain (kg) that is equivalent to pregnancy weight gain z-scores at 40 wk. Severity-weighted RRs (95% confidence intervals) have been adjusted for participant’s age, education, race/ethnicity, marital status, prepregnancy smoking, gravidity, medical insurance, chronic hypertension, diet quality, physical activity, nausea and vomiting, binge drinking, sleep satisfaction, depressive symptoms, anxiety, neighborhood walkability, neighborhood deprivation, proximity to grocery stores, and percent of neighborhood with income below the poverty line. For gestational diabetes and preeclampsia cases, the total weight gain before diagnosis was used to calculate pregnancy weight gain z-scores. CI, confidence interval.

FIGURE 3

Discussion

In this large United States cohort of nulliparous pregnancies with 2‒7 y postpartum follow-up, we found that individuals who gained less weight than what is currently recommended by the IOM did not have a meaningful increase in the risk of a composite of 10 maternal and child health conditions. These findings support arguments to decrease or even remove the lower limit of the recommended ranges for individuals with prepregnancy overweight and obesity.

The lower limits of the IOM-recommended range for individuals with overweight or obesity were based on limited and indirect evidence on the harms of low weight gain. There were concerns that low pregnancy weight gain increased the risk of impaired child neurodevelopment due to maternal ketosis, as well as stillbirth and fetal growth restriction [10]. A new systematic review [67] found no conclusive evidence of an association between pregnancy weight gain and child neurodevelopment, and research on pregnancy weight gain and stillbirth remains limited. Evidence on fetal growth restriction was based on studies of small-for-gestational age birth; findings that low pregnancy weight gain is associated with higher risk of small-for-gestational age was important in establishing the lower limit. Notably, in our study, the increased risk of small-for-gestational age birth with low pregnancy weight gain was greatly outweighed by the frequency of outcomes associated with high weight gain, including excess postpartum weight, preeclampsia, and maternal metabolic syndrome. A recent systematic review drew similar conclusions [12]. Finally, the IOM was concerned that low pregnancy weight gain in individuals with a high BMI could be a marker of poor diet quality or fasting. Nevertheless, we found a few differences in diet quality in participants with low weight gain compared with those who gained within the current guidelines.

Determining optimal weight gain ranges requires the simultaneous consideration of a comprehensive range of perinatal and longer-term maternal and child health outcomes. Studies to date, however, have only included a limited number of outcomes. In an individual participant-level meta-analysis, investigators created a composite adverse outcome consisting of only 6 short-term perinatal outcomes (preeclampsia, gestational diabetes, cesarean delivery, preterm birth, and small- or large-for-gestational-age birth) and no longer-term outcomes [68], and did not consider the seriousness of each outcome. Consequently, results inevitably favor weight gain ranges that reduce the risk of the most common but less serious outcomes [69]. In a Massachusetts cohort, the lowest adjusted risk of a severity-weighted (determined by a sample of 12 researchers) composite of 5 adverse outcomes (preterm birth, SGA birth, large-for-gestational-age birth, child obesity, and 1-y postpartum weight retention) occurred at total weight gains at or below the lower limit of the guidelines (6 kg for overweight, −7.6 kg for obesity) [70]. Using a Brazilian cohort, investigators reported that optimal total weight gain for reducing the risk of a weighted composite of 4 outcomes (small- and large-for-gestational-age birth, preterm birth, 1-y postpartum weight retention) was ∼7–11 kg and 5–9 kg for pregnancies affected by overweight or obesity, respectively [71].

In a recent article, we examined the safety of low weight gain or weight loss by obesity class among 15,760 Swedish individuals with obesity, for a severity-weighted composite outcome of 10 maternal and child short- and long-term health outcomes, including perinatal death [72]. In this previous study, we found that, compared with the IOM’s recommended lower limit, there was no increased risk associated with low weight gain or weight loss in class 1 or 2 obesity, and lower risks for class 3. The results for class 1 and 2 obesities in this Swedish cohort were strikingly similar to those we observed in the present study of predominantly individuals with class 1 or 2 obesity. The similarity of findings with the Swedish study lends support for the generalizability of our findings from this racially and socioeconomically diverse United States cohort of nulliparous pregnancies.

Although our findings suggest that lower pregnancy weight gain among participants with a high prepregnancy BMI should be considered, gaining less weight is challenging, given the United States built environment. The majority of pregnant individuals in the United States with overweight or obesity gain above IOM recommendations [73]. Randomized trials of lifestyle interventions in individuals with obesity have shown that it is possible to restrict weight gain, with ∼2‒7 kg lower weight gain in the intervention arms, leading to total weight gains of 5‒8 kg [[14], [15], [16], [17], [18]]. Nevertheless, these weight gains required intensive interventions, and identifying more scalable strategies to reduce weight gain and structural changes needed to support healthy weight are important future research directions. Our findings can be used to set target pregnancy weight gain values for such trials.

A strength of our study is the inclusion of 10 short- and longer-term maternal and child health outcomes associated with pregnancy weight gain. The small number of perinatal deaths, however, is notable, and other outcomes may be relevant, particularly those beyond 3 y postpartum. The severity weights we used are not definitive, but previous work by our team in individuals with normal weight found that associations were robust to varying the severity weights [22]. Our sample was too small to stratify by obesity class, but determining optimal weight gain according to obesity severity is a high public health priority. Our study can only suggest associations; it cannot determine causality. Although our adjustment for a range of confounders, including diet and physical activity, lessens the likelihood of confounding, covariate measurement error or unmeasured factors such as wealth or other social determinants of health may lead to bias. Although the characteristics of the cohort with and without follow-up data were nearly identical, we cannot rule out the potential for selection bias. Our results may not be generalizable to all pregnant individuals in the United States, but we believe that they are valuable given the size and socioeconomic and racial/ethnic diversity of the cohort.

Our data suggest that a reevaluation of the lower limit of the 2009 IOM recommendations for pregnancy weight gain among pregnancies with overweight or obesity is warranted. Studies with larger samples of pregnancies with low weight gain and weight loss are needed to draw firm conclusions on the safety of lowering the lower limit of weight gain guidelines. Our findings, however, contribute to an emerging body of evidence that weight gain below the lower limit of recommended weight gain ranges in these prepregnancy BMI groups may be safe. Decreasing the lower limit of pregnancy weight gain guidelines for individuals with a high prepregnancy BMI should be considered.

Author contributions

The authors’ responsibilities were as follows – LMB, KJ, BA, and JAH designed research; LMB, KJ, and JAH conducted research and wrote the article; LMB, SMP, and JAH analyzed data or performed statistical analysis; KPH, DK, BA, and SMP provided critical feedback on the article; LMB had primary responsibility for final content; and all authors: read and approved the final manuscript.

Conflict of interest

DK is the team leader of ExpertLens at RAND. ExpertLens is the platform used to collect data for this study. DK was a Delphi method consultant to Pfizer in 2022–2023. All other authors have nothing to disclose.

Funding

This study is supported by grant funding from the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD): R01 HD094777 to LMB and JAH, as well as U10 HD063036; U10 HD063072; U10 HD063047; U10 HD063037; U10 HD063041; U10 HD063020; U10 HD063046; U10 HD063048; and U10 HD063053. This study is also supported by cooperative agreement funding from the National Heart, Lung, and Blood Institute and the Eunice Kennedy Shriver National Institute of Child Health and Human Development: U10 HL119991; U10 HL119989; U10 HL120034; U10 HL119990; U10 HL120006; U10 HL119992; U10 HL120019; U10 HL119993; and U10 HL120018. Support was also provided by the National Institutes of Health: Office of Research on Women’s Health through U10 HL119991; Office of Behavioral and Social Sciences Research through U10 HL119991 and U10-HL119992; and the National Center for Advancing Translational Sciences through UL 1TR000124, UL 1TR000153, UL 1TR000439, and UL 1TR001108; and the Barbra Streisand Women’s Cardiovascular Research and Education Program, and the Erika J. Glazer Women’s Heart Research Initiative, Cedars-Sinai Medical Center, Los Angeles. Support was also provided by respective Clinical and Translational Science Institutes to Indiana University (UL1TR001108) and the University of California Irvine (UL1TR000153). JAH holds a Canada Research Chair in Perinatal Population Health from the Federal Government of Canada.

The funders had no role in the study design, data collection and analysis, decision to publish, or preparation of the manuscript.

Data availability

The Nulliparous Pregnancy Outcomes Study: monitoring mothers-to-be data described in the manuscript, as well as the code book, are publicly and freely available without restriction at https://dash.nichd.nih.gov/study/226675. The study investigators and the Data Coordinating and Analysis Center have copies of the entire database but cannot release that version to outside investigators due to the permissions granted by the participants during the consent process and to protect participant confidentiality. The nuMoM2b-HHS data described in the manuscript are available from the data coordinating center on reasonable request. Code for replication purposes can be found at https://osf.io/amg95/.

Appendix A Supplementary data

The following is the Supplementary data to this article:Multimedia component 1

Multimedia component 1

Appendix A Supplementary data to this article can be found online at https://doi.org/10.1016/j.ajcnut.2024.06.011.
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References

1 Deputy N.P. Dub B. Sharma A.J. Prevalence and trends in prepregnancy normal weight – 48 sstates, New York City, and District of Columbia, 2011–2015 MMWR Morb. Mortal. Wkly. Rep. 66 51–52 2018 1402 1407 10.15585/mmwr.mm665152a3 29300720
2 Vats H. Saxena R. Sachdeva M.P. Walia G.K. Gupta V. Impact of maternal pre-pregnancy body mass index on maternal, fetal and neonatal adverse outcomes in the worldwide populations: a systematic review and meta-analysis Obes. Res. Clin. Pract. 15 6 2021 536 545 10.1016/j.orcp.2021.10.005 34782256
3 D’Souza R. Horyn I. Pavalagantharajah S. Zaffar N. Jacob C.-E. Maternal body mass index and pregnancy outcomes: a systematic review and metaanalysis Am. J. Obstet. Gynecol. MFM. 1 4 2019 100041 10.1016/j.ajogmf.2019.100041
4 Catalano P.M. Shankar K. Obesity and pregnancy: mechanisms of short term and long term adverse consequences for mother and child BMJ 356 2017 j1 10.1136/bmj.j1 28179267
5 Andersen C.H. Thomsen P.H. Nohr E.A. Lemcke S. Maternal body mass index before pregnancy as a risk factor for ADHD and autism in children Eur. Child Adolesc. Psychiatry. 27 2 2018 139 148 10.1007/s00787-017-1027-6 28712019
6 Razaz N. Villamor E. Muraca G.M. Bonamy A.E. Cnattingius S. Maternal obesity and risk of cardiovascular diseases in offspring: a population-based cohort and sibling-controlled study Lancet Diabetes Endocrinol 8 7 2020 572 581 10.1016/S2213-8587(20)30151-0 32559473
7 Kuhle S. Muir A. Woolcott C.G. Brown M.M. McDonald S.D. Abdolell M. Maternal pre-pregnancy obesity and health care utilization and costs in the offspring Int. J. Obes. (Lond). 43 4 2019 735 743 10.1038/s41366-018-0149-3 30006584
8 Chu S.Y. Bachman D.J. Callaghan W.M. Whitlock E.P. Dietz P.M. Berg C.J. Association between obesity during pregnancy and increased use of health care N. Engl. J. Med. 358 14 2008 1444 1453 10.1056/NEJMoa0706786 18385496
9 Sagi-Dain L. Obesity in pregnancy: ACOG practice bulletin, Number 230 Obstet. Gynecol. 137 6 2021 e128 e144 10.1097/AOG.0000000000004527 34011890
10 Institute of Medicine Weight Gain During Pregnancy: Reexamining the Guidelines National Academies 2009 Press Washington, DC
11 Artal R. Lockwood C.J. Brown H.L. Weight gain recommendations in pregnancy and the obesity epidemic Obstet. Gynecol. 115 1 2010 152 155 10.1097/AOG.0b013e3181c51908 20027048
12 Mustafa H.J. Seif K. Javinani A. Aghajani F. Orlinsky R. Alvarez M.V. Ryan A. Gestational weight gain below instead of within the guidelines per class of maternal obesity: a systematic review and meta-analysis of obstetrical and neonatal outcomes Am. J. Obstet. Gynecol. MFM. 4 5 2022 100682 10.1016/j.ajogmf.2022.100682
13 Barbour L.A. Weight gain in pregnancy: is less truly more for mother and infant? Obstet Med 5 2 2012 58 64 10.1258/om.2012.120004
14 Claesson I.M. Sydsjö G. Brynhildsen J. Cedergren M. Jeppsson A. Nyström F. Weight gain restriction for obese pregnant women: a case–control intervention study BJOG 115 1 2008 44 50 10.1111/j.1471-0528.2007.01531.x 17970795
15 Wolff S. Legarth J. Vangsgaard K. Toubro S. Astrup A. A randomized trial of the effects of dietary counseling on gestational weight gain and glucose metabolism in obese pregnant women Int. J. Obes. (Lond). 32 3 2008 495 501 10.1038/sj.ijo.0803710 18227847
16 Vesco K.K. Karanja N. King J.C. Gillman M.W. Leo M.C. Perrin N. Efficacy of a group-based dietary intervention for limiting gestational weight gain among obese women: a randomized trial Obesity (Silver Spring) 22 9 2014 1989 1996 10.1002/oby.20831 25164259
17 Ferrara A. Hedderson M.M. Brown S.D. Albrigh C.L. Ehrlich S.F. Tsai A.L. The comparative effectiveness of diabetes prevention strategies to reduce postpartum weight retention in women with gestational diabetes mellitus: the gestational diabetes’ effects on moms (GEM) cluster randomized controlled trial Diabetes Care 39 1 2016 65 74 10.2337/dc15-1254 26657945
18 Van Horn L. Peaceman A. Kwasny M. Vincent E. Fought A. Josefson J. Dietary approaches to stop hypertension diet and activity to limit gestational weight: maternal offspring metabolics family intervention trial, a technology enhanced randomized trial Am. J. Prev. Med. 55 5 2018 603 614 10.1016/j.amepre.2018.06.015 30262148
19 Haas D.M. Parker C.B. Wing D.A. Parry S. Grobman W.A. Mercer B.M. A description of the methods of the nulliparous pregnancy outcomes study: monitoring mothers-to-be (nuMoM2b) Am. J. Obstet. Gynecol. 212 4 2015 539 e1 539 e24 10.1016/j.ajog.2015.01.019
20 Haas D.M. Ehrenthal D.B. Koch M.A. Catov J.M. Barnes S.E. Facco F. Pregnancy as a window to future cardiovascular health: design and implementation of the nuMoM2b heart health study Am. J. Epidemiol. 183 6 2016 519 530 10.1093/aje/kwv309 26825925
21 Catov J.M. McNeil R.B. Marsh D.J. Mercer B.M. Bairey Merz C.N. Parker C.B. Early pregnancy atherogenic profile in a first pregnancy and hypertension risk 2 to 7 years after delivery J. Am. Heart Assoc. 10 5 2021 e017216 10.1161/JAHA.120.017216
22 Bodnar L.M. Johansson K. Himes K.P. Khodyakov D. Abrams B. Parisi S.M. Hutcheon J.A. Do current pregnancy weight gain guidelines balance risks of adverse maternal and child health in a United States cohort? Am. J. Clin. Nutr. 119 2 2024 527 536 10.1016/j.ajcnut.2023.10.015 38182445
23 Hutcheon J.A. Bodnar L.M. Good practices for observational studies of maternal weight and weight gain in pregnancy Paediatr. Perinat. Epidemiol. 32 2 2018 152 160 10.1111/ppe.12439 29345321
24 Hutcheon J.A. Platt R.W. Abrams B. Himes K.P. Simhan H.N. Bodnar L.M. Pregnancy weight gain charts for obese and overweight women Obesity (Silver Spring) 23 3 2015 532 535 10.102/oby.21011 25707378
25 Siega-Riz A.M. Viswanathan M. Moos M.K. Deierlein A. Mumford S. Knaack J. A systematic review of outcomes of maternal weight gain according to the Institute of Medicine recommendations: birthweight, fetal growth, and postpartum weight retention Am. J. Obstet. Gynecol. 201 4 2009 339.e1 10.1016/j.ajog.2009.07.002 14
26 Hutcheon J.A. Stephansson O. Cnattingius S. Bodnar L.M. Wikström A.K. Johansson K. Pregnancy weight gain before diagnosis and risk of preeclampsia: a population-based cohort study in nulliparous women Hypertension 72 2 2018 433 441 10.1161/HYPERTENSIONAHA.118.10999 29915016
27 MacDonald S.C. Bodnar L.M. Himes K.P. Hutcheon J.A. Patterns of gestational weight gain in early pregnancy and risk of gestational diabetes mellitus Epidemiology 28 3 2017 419 427 10.1097/EDE.0000000000000629 28151742
28 Fraser A. Tilling K. Macdonald-Wallis C. Hughes R. Sattar N. Nelson S.M. Associations of gestational weight gain with maternal body mass index, waist circumference, and blood pressure measured 16 y after pregnancy: the Avon Longitudinal Study of Parents and Children (ALSPAC) Am. J. Clin. Nutr 93 6 2011 1285 1292 10.3945/ajcn.110.008326 21471282
29 Mamun A.A. O'Callaghan M. Callaway L. Williams G. Najman J. Lawlor D.A. Associations of gestational weight gain with offspring body mass index and blood pressure at 21 years of age: evidence from a birth cohort study Circulation 119 13 2009 1720 1727 10.1161/CIRCULATIONAHA 19307476
30 Xu H. Hutcheon J.A. Liu X. Stephansson O. Cnattingius S. Arkema E.V. Johansson K. Risk of gestational diabetes mellitus in relation to early pregnancy and gestational weight gain before diagnosis: a population-based cohort study Acta Obstet. Gynecol. Scand. 101 11 2022 1253 1261 10.1111/aogs.14450 36069213
31 Voerman E. Santos S. Patro Golab B. Amiano P. Ballester F. Barros H. Maternal body mass index, gestational weight gain, and the risk of overweight and obesity across childhood: an individual participant data meta-analysis PLoS Med 16 2 2019 e1002744 10.1371/journal.pmed.1002744
32 Goldstein R.F. Abell S.K. Ranasinha S. Misso M. Boyle J.A. Black M.H. Association of gestational weight gain with maternal and infant outcomes: a systematic review and meta-analysis JAMA 317 21 2017 2207 2225 10.1001/jama.2017.3635 28586887
33 Nehring I. Schmoll S. Beyerlein A. Hauner H. von Kries R. Gestational weight gain and long-term postpartum weight retention: a meta-analysis Am. J. Clin. Nutr. 94 5 2011 1225 1231 10.3945/ajcn.111.015289 21918221
34 Oteng-Ntim E. Varma R. Croker H. Poston L. Doyle P. Lifestyle interventions for overweight and obese pregnant women to improve pregnancy outcome: systematic review and meta-analysis BMC Med 10 2012 47 10.1186/1741-7015-10-47 22574949
35 Thangaratinam S. Rogozinska E. Jolly K. Glinkowski S. Roseboom T. Tomlinson J.W. Effects of interventions in pregnancy on maternal weight and obstetric outcomes: meta-analysis of randomised evidence BMJ 344 2012 e2088 10.1136/bmj.e2088
36 Mannan M. Doi S.A. Mamun A.A. Association between weight gain during pregnancy and postpartum weight retention and obesity: a bias-adjusted meta-analysis Nutr. Rev. 71 6 2013 343 352 10.1111/nure.12034 23731445
37 McClure C.K. Catov J.M. Ness R. Bodnar L.M. Associations between gestational weight gain and BMI, abdominal adiposity, and traditional measures of cardiometabolic risk in mothers 8 y postpartum Am. J. Clin. Nutr. 98 5 2013 1218 1225 10.3945/ajcn.112.055772 24047920
38 Karachaliou M. Georgiou V. Roumeliotaki T. Chalkiadaki G. Daraki V. Koinaki S. Association of trimester-specific gestational weight gain with fetal growth, offspring obesity, and cardiometabolic traits in early childhood Am. J. Obstet. Gynecol. 212 4 2015 502.e1 502.e14 10.1016/j.ajog.2014.12.038
39 Santos S. Voerman E. Amiano P. Barros H. Beilin L.J. Bergström A. Impact of maternal body mass index and gestational weight gain on pregnancy complications: an individual participant data meta-analysis of European, North American and Australian cohorts BJOG 126 8 2019 984 995 10.1111/1471-0528.15661 30786138
40 Bodnar L.M. Khodyakov D. Himes K.P. Burke J.G. Parisi S. Hutcheon J.A. Engaging patients and professionals to evaluate the seriousness of maternal and child health outcomes: protocol for a modified Delphi Study JMIR Res. Protoc. 9 6 2020 e16478 10.2196/16478
41 ACOG Practice Bulletin No. 190: gestational diabetes mellitus Obstet. Gynecol. 131 2 2018 e49 e64 10.1097/AOG.0000000000002501 29370047
42 Facco F.L. Parker C.B. Reddy U.M. Silver R.M. Koch M.A. Louis J.M. Association between sleep-disordered breathing and hypertensive disorders of pregnancy and gestational diabetes mellitus Obstet. Gynecol. 129 1 2017 31 41 10.1097/AOG.0000000000001805 27926645
43 Hypertension in Pregnancy Report of the American College of Obstetricians and Gynecologists’ Task Force on hypertension in pregnancy Obstet. Gynecol. 122 5 2013 1122 1131 10.1097/01.AOG.0000437382.03963.88 24150027
44 Grundy S.M. Cleeman J.I. Daniels S.R. Donato K.A. Eckel R.H. Franklin B.A. Diagnosis and management of the metabolic syndrome: an American Heart Association/National Heart, Lung, and Blood Institute Scientific Statement Circulation 112 17 2005 2735 2752 10.1161/CIRCULATIONAHA.105.169404 16157765
45 Grantz K.L. Kim S. Grobman W.A. Newman R. Owen J. Skupski D. Fetal growth velocity: the NICHD fetal growth studies Am. J. Obstet. Gynecol. 219 3 2018 285.e1 285.e36 10.1016/j.ajog.2018.05.016
46 WHO Multicentre Growth Reference Study Groupde Onis M. WHO Child Growth Standards based on length/height, weight and age Acta Paediatr 450 Suppl 2006 76 85 10.1111/j.1651-2227.2006.tb02378.x
47 Bodnar L.M. Khodyakov D. Parisi S.M. Himes K.P. Burke J.G. Hutcheon J.A. Rating the seriousness of maternal and child health outcomes linked with pregnancy weight gain, Paediatr Perinat. Epidemiol. 35 4 2021 459 468 10.1111/ppe.12741
Bodnar L.M. Hutcheon J.A. Are detailed behavioral, psychosocial, and environmental variables necessary to control for confounding in pregnancy weight gain research? Epidemiology 34 1 2023 56 63 10.1097/EDE.0000000000001556 36455246
49 Hernán M.A. Hernández-Díaz S. Werler M.M. Mitchell A.A. Causal knowledge as a prerequisite for confounding evaluation: an application to birth defects epidemiology Am. J. Epidemiol. 155 2 2002 176 184 10.1093/aje/155.2.176 11790682
50 Koren G. Boskovic R. Hard M. Maltepe C. Navioz Y. Einarson A. Motherisk-PUQE (pregnancy-unique quantification of emesis and nausea) scoring system for nausea and vomiting of pregnancy Am. J. Obstet. Gynecol. 186 5 Suppl Understanding 2002 S228 S231 10.1067/mob.2002.123054 12011891
51 Krebs-Smith S.M. Pannucci T.E. Subar A.F. Kirkpatrick S.I. Lerman J.L. Tooze J.A. Update of the healthy eating index: HEI–2015 J. Acad. Nutr. Diet. 118 9 2018 1591 1602 10.1016/j.jand.2019.07.025 30146071
52 Piercy K.L. Troiano R.P. Ballard R.M. Carlson S.A. Fulton J.E. Galuska D.A. The physical activity guidelines for Americans JAMA 320 19 2018 2020 2028 10.1001/jama.2018.14854 30418471
53 Levine D.W. Dailey M.E. Rockhill B. Tipping D. Naughton M.J. Shumaker S.A. Validation of the women’s health initiative insomnia rating scale in a multicenter controlled clinical trial Psychosom. Med. 67 1 2005 98 104 10.1097/01.psy.0000151743.58067.f0 15673630
54 Cox J.L. Chapman G. Murray D. Jones P. Validation of the Edinburgh Postnatal Depression Scale (EPDS) in non-postnatal women J. Affect. Disord. 39 3 1996 185 189 10.1016/0165-0327(96)00008-0 8856422
55 Spielberger C.D. Gorsuch R.L. Lushene R.E. Manual for State-Trait Anxiety Inventory (Self-Evaluation Questionnaire) 1970 Consulting Psychologists Press Palo Alto, CA
56 Thomas J. Zeller L. National Walkability Index User Guide and Methodology 2017 Environmental Protection Agency Washington, DC, USA
57 Connor K.M. Davidson J.R. Development of a new resilience scale: the Connor–Davidson Resilience Scale (CD-RISC) Depress. Anxiety. 18 2 2003 76 82 10.1002/da.10113 12964174
58 Kind A.J.H. Buckingham W.R. Making neighborhood-disadvantage metrics accessible – the neighborhood atlas N. Engl. J. Med. 378 26 2018 2456 2458 10.1056/NEJMp1802313 29949490
59 Reedy J. Lerman J.L. Krebs-Smith S.M. Kirkpatrick S.I. Pannucci T.E. Wilson M.M. Evaluation of the Healthy Eating Index–2015 J. Acad. Nutr. Diet. 118 9 2018 1622 1633 10.1016/j.jand.2018.05.019 30146073
60 Royston P. Multiple imputation of missing values: further update of ice, with an emphasis on categorical variables Stata. J. 9 3 2009 466 477 10.1177/1536867X0900900308
61 Hutcheon J.A. Bodnar L.M. Platt R.W. Using perinatal morbidity scoring tools as a primary study outcome J. Epidemiol. Community Health. 71 11 2017 1090 1093 10.1136/jech-2017-209419 29038316
62 Harrell F.E. Jr. Lee K.L. Pollock B.G. Regression models in clinical studies: determining relationships between predictors and response J. Natl. Cancer Inst. 80 15 1988 1198 1202 10.1093/jnci/80.15.1198 3047407
63 Sterne J.A. White I.R. Carlin J.B. Spratt M. Royston P. Kenward M.G. Multiple imputation for missing data in epidemiological and clinical research: potential and pitfalls BMJ 338 2009 b2393 10.1136/bmj.b2393 19564179
64 Schomaker M. Heumann C. Bootstrap inference when using multiple imputation Stat. Med. 37 14 2018 2252 2266 10.1002/sim.7654 29682776
65 Wasserstein R.L. Lazar N.A. The ASA statement on p-values: context, process, and purpose Am. Stat. 70 2 2016 129 133 10.1080/00031305.2016.1154108
66 Greenland S. Senn S.J. Rothman K.J. Carlin J.B. Poole C. Goodman S.N. Statistical tests, P values, confidence intervals, and power: a guide to misinterpretations Eur. J. Epidemiol. 31 4 2016 337 350 10.1007/s10654-016-0149-3 27209009
67 Martínez-Hortelano J.A. Álvarez-Bueno C. Cavero-Redondo I. Herráiz-Adillo Á. Berlanga-Macías C. Martínez-Vizcaíno V. Gestational weight gain and offspring’s cognitive skills: a systematic review and meta-analysis BMC Pediatr 20 1 2020 533 10.1186/s12887-020-02429-7 33243183
68 Voerman E. Santos S. Inskip H. Amiano P. Barros H. Charles M.A. Association of gestational weight gain with adverse maternal and infant outcomes JAMA 321 17 2019 1702 1715 10.1001/jama.2019.3820 31063572
69 Bodnar L.M. Himes K.P. Hutcheon J.A. Optimal gestational weight gain JAMA 322 11 2019 1106 1107 10.1001/jama.2019.10946
70 Oken E. Kleinman K.P. Belfort M.B. Hammitt J.K. Gillman M.W. Associations of gestational weight gain with short- and longer-term maternal and child health outcomes Am. J. Epidemiol. 170 2 2009 173 180 10.1093/aje/kwp101 19439579
71 Carrilho T.R.B. Hutcheon J.A. Rasmussen K.M. Reichenheim M.E. Farias D.R. Freitas-Costa N.C. Gestational weight gain according to the Brazilian charts and its association with maternal and infant adverse outcomes Am. J. Clin. Nutr. 117 2 2023 414 425 10.1016/j.ajcnut.2022.11.021 36811564
72 Johansson K. Bodnar L.M. Stephansson O. Abrams B. Hutcheon J.A. Safety of low weight gain or weight loss in pregnancies with class 1, 2, and 3 obesity: a population-based cohort study Lancet 403 10435 2024 1472 1481 10.1016/S0140-6736(24)00255-1 38555927
73 Deputy N.P. Sharma A.J. Kim S.Y. Hinkle S.N. Prevalence and characteristics associated with gestational weight gain adequacy Obstet. Gynecol. 125 4 2015 773 781 10.1097/AOG.0000000000000739 25751216
