Gestational Weight Gain-Re-Examining the Current Paradigm

Rethinking causal assumptions about maternal BMI, gestational weight gain, and adverse pregnancy outcomes

BACKGROUND

The aim of this study was to evaluate commonly assumed causal relationships between body mass index (BMI), gestational weight gain (GWG), and adverse pregnancy outcomes, which have formed the basis of guidelines and interventions aimed at limiting GWG in women with overweight or obesity. We explored relationships between maternal BMI, total GWG (as a continuous variable and as 'excessive' GWG), and pregnancy outcomes (including infant birthweight measures and caesarean birth).

METHODS

Analysis of individual participant data (IPD) from the i-WIP (International Weight Management in Pregnancy) Collaboration, from randomised trials of diet and/or physical activity interventions during pregnancy reporting GWG and maternal and neonatal outcomes. Women randomised to the control arm of 20 eligible randomised trials (4370 of 8908 participants) from the i-WIP dataset of 36 randomised trials (total 12,240 women). The main research questions were to characterise the relationship between maternal BMI and (a) total GWG, (b) the risk of 'excessive' GWG (using the Institute of Medicine's guidelines), and (c) adverse pregnancy outcomes as mediated via GWG versus other pathways to determine the extent to which the observed effect of maternal BMI on pregnancy outcomes is mediated via GWG. We utilised generalised linear models and regression-based mediation analyses within an IPD meta-analysis framework.

RESULTS

Mean GWG decreased linearly as maternal BMI increased; however, the risk of 'excessive' GWG increased markedly at BMI category thresholds (i.e. between the normal and overweight BMI category threshold and between the overweight and obese BMI category threshold). Increasing maternal BMI was associated with increased risk of all pregnancy outcomes assessed; however, there was no evidence that this effect was mediated via effects on GWG.

CONCLUSIONS

There is evidence of a meaningful relationship between maternal BMI and GWG and between maternal BMI and adverse pregnancy outcomes. There is no evidence that the effect of maternal BMI on outcomes is via an effect on GWG. Our analyses also cast doubt on the existence of a relationship between 'excessive' GWG and adverse pregnancy outcomes. Our findings challenge the practice of actively managing GWG throughout pregnancy.

Physical Activity during Preconception Impacts Some Maternal Outcomes-A Cross-Sectional Study on a Population of Polish Women

BACKGROUND

Physical activity is an element of a healthy lifestyle and is safe in most pregnancies. The aim of this study was to assess the impact of physical activity levels before and during pregnancy on pregnancy outcomes for both the mother and child.

METHODS

A cross-sectional survey was conducted on a population of Polish women. An anonymous questionnaire was distributed electronically via maternity and parental Facebook groups.

RESULTS

The final research group included 961 women. The analysis showed that physical activity 6 months before pregnancy was associated with a lower risk of gestational diabetes mellitus (GDM), but physical activity during pregnancy showed no such association. In all, 37.8% of women with low activity in the first trimester, in comparison to 29.4% of adequately active women, gained an excessive amount of weight during pregnancy (p = 0.0306). The results showed no association between activity level and pregnancy duration, type of delivery or newborn birth weight.

CONCLUSIONS

Our study indicates that physical activity during the preconception period is crucial to GDM occurrence.

Analysis and Comparison of Early Childhood Nutritional Outcomes Among Offspring of Chinese Women Under the Chinese 2021 and US 2009 Gestational Weight Gain Guidelines

IMPORTANCE

In 2009, the US National Academy of Medicine (NAM) released revised gestational weight gain (GWG) guidelines, which were established primarily for White North American women and may be unsuitable for Asian women. In 2021, the Chinese Nutrition Society (CNS) released its GWG guidelines, but their applicability requires re-examination.

OBJECTIVE

To compare the differences between the CNS and NAM recommendations for GWG in association with health outcomes in the offspring of Chinese women.

DESIGN, SETTING, AND PARTICIPANTS

In this bidirectional cohort study, children in China were recruited at age 3 years from 2017 to 2018, with 2 follow-up visits over the next 2 years (between September 2017 and September 2020). Information during pregnancy was retrieved from medical records. Data analysis was performed from October 2021 to January 2022.

MAIN OUTCOMES AND MEASURES

GWG was classified as insufficient, appropriate, or excessive according to the CNS and NAM guidelines separately. Children's height, weight, fat mass, fat-free mass, and percentage of body fat were measured at each visit. Body mass index, fat mass index, fat-free mass index, weighted κ score, risk ratio values, sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) were calculated.

RESULTS

A total of 3822 children (1996 boys and 1826 girls; mean [SD] age, 3.79 [0.30] years) were enrolled; after exclusions, 3170 term singleton children were recruited and were followed at 4 and 5 years of age. According to the CNS guidelines, the prevalence rates were 14.1% for insufficient GWG, 48.1% for appropriate GWG, and 37.9% for excessive GWG, whereas the rates according to NAM guidelines were 39.7% for insufficient GWG, 37.2% for appropriate GWG, and 23.1% for excessive GWG. The weighted κ value for the classification agreement between the 2 guidelines was 0.530 (95% CI, 0.510-0.550). For the appropriate GWG group, the rates for low nutritional levels did not differ between the 2 guidelines, but the rates for high nutritional levels were significantly lower under CNS guidelines than under NAM guidelines. When the sensitivity, specificity, PPV, and NPV with respect to the mothers who maintained appropriate GWG were used to estimate the nonhigh nutritional status of their offspring, generally higher values based on the CNS guidelines were found compared with those based on the NAM recommendations.

CONCLUSIONS AND RELEVANCE

These findings suggest that the GWG recommendations promulgated by the NAM are higher than the CNS guidelines, with the latter more suitable for Chinese women.

Maternal overweight and obesity during pregnancy: strategies to improve outcomes for women, babies, and children

INTRODUCTION

Women with overweight and obesity, and their children, are at increased risk of adverse pregnancy, birth, and longer term health outcomes, believed to be compounded by excessive gestational weight gain (GWG). Research to date has focused on interventions to reduce excessive GWG through changes to maternal diet and/or lifestyle.

AREAS COVERED

Current clinical recommendations for GWG vary according to a woman's early pregnancy body mass index, based on assumptions that associations between GWG and adverse pregnancy outcomes are causal in nature, and modifiable. While there are small differences in GWG following pregnancy interventions, there is little evidence for clinically relevant effects on pregnancy, birth, and longer term childhood outcomes. This review considers interventional studies targeting women with overweight or obesity to reduce GWG in an effort to improve maternal and infant health, and the current evidence for interventions prior to conception.

EXPERT OPINION

GWG is not modifiable via diet and lifestyle change, and continued efforts to find the 'right' intervention for women with overweight and obesity during pregnancy are unjustified. Researchers should focus on gathering evidence for interventions prior to pregnancy to optimize maternal health and weight to improve pregnancy, birth, and longer term health outcomes associated with obesity.

Gestational weight gain during the second and third trimesters and adverse pregnancy outcomes, results from a prospective pregnancy cohort in urban Tanzania

Background

Appropriate gestational weight gain (GWG) is important for optimal pregnancy outcomes. This study prospectively evaluated the associations between GWG during the second and third trimesters of pregnancy and adverse pregnancy outcomes in an urban Tanzanian pregnancy cohort.

Methods

We used data from a randomized clinical trial conducted among pregnant women recruited by 27 weeks of gestation in Dar es Salaam, Tanzania (N = 1230). Women’s gestational weight was measured at baseline and at monthly antenatal visits. Weekly GWG rate during the second and third trimesters was calculated and characterized as inadequate, adequate, or excessive, in conjunction with measured or imputed early-pregnancy BMI status according to the 2009 Institute of Medicine (IOM) GWG guidelines. We used multivariable Poisson regression with a sandwich variance estimator to calculate risk ratios (RR) for associations of GWG with low birth weight, preterm birth, small for gestational age (SGA), and large for gestational age (LGA). Degree of appropriate GWG defined using additional metrics (i.e., percentage of adequacy, z-score) and potential effect modification by maternal BMI were additionally evaluated.

Results

According to the IOM guidelines, 517 (42.0%), 270 (22.0%), and 443 (36.0%) women were characterized as having inadequate, adequate, and excessive GWG, respectively. Overall, compared to women with adequate GWG, women with inadequate GWG had a lower risk of LGA births (RR = 0.54, 95% CI: 0.36–0.80) and a higher risk of SGA births (RR = 1.32, 95% CI: 0.95–1.81). Women with inadequate GWG as defined by percentage of GWG adequacy had a higher risk of LBW (OR = 1.93, 95% CI: 1.03–3.63). In stratified analyses by early-pregnancy BMI, excessive GWG among women with normal BMI was associated with a higher risk of preterm birth (RR = 1.59, 95% CI: 1.03–2.44).

Conclusions

A comparatively high percentage of excessive GWG was observed among healthy pregnant women in Tanzania. Both inadequate and excessive GWGs were associated with elevated risks of poor pregnancy outcomes. Future studies among diverse SSA populations are warranted to confirm our findings, and clinical recommendations on optimal GWG should be developed to promote healthy GWG in SSA settings.

Trial registration: This trial was registered as “Prenatal Iron Supplements: Safety and Efficacy in Tanzania” (NCT01119612; http://clinicaltrials.gov/show/NCT01119612).

Supplementary Information

The online version contains supplementary material available at 10.1186/s12978-022-01441-7.

Pregnancy is a critical lifetime event for both mother and the offspring, with implications in short-term and long-term health consequences. Gestational weight gain (GWG) is an important modifiable factor for pregnancy outcomes related to infant body size and weight and prematurity. Countries in sub-Saharan Africa (SSA) have long had poor rates of insufficient GWG and pregnancy complications associated with insufficient GWG. Nevertheless, some SSA countries are experiencing economic transitions accompanied with changes in lifestyle and nutrition, which might impact pregnancy experiences, including GWG and pregnancy outcomes. This study aimed to characterize recent GWG patterns and the associations of both inadequate and excessive GWG with adverse pregnancy outcomes, using an urban pregnancy cohort in Tanzania. This study found that 42.0%. 22.0%, and 36.0% of women had insufficient, adequate, and excessive GWG, respectively. Insufficient GWG was associated with higher risks of small infant size and low infant body weight, and excessive GWG was associated with higher risk of preterm birth, particularly among women with body mass index 18.5–25.0 kg/m². Results from the present study highlight that both insufficient and excessive GWG are of potential public health concerns in urban centers of SSA, concerning upward trends in obesity and possibly obesity-related pregnancy consequences. Local public health practitioners should continue to advocate longitudinal GWG monitoring and care among African pregnant women, and optimal GWG with feasible and effective clinical guidelines should be developed to prevent both over- and under-gaining of maternal weight during pregnancy.

Body Composition in Preschool Children and the Association With Prepregnancy Weight and Gestational Weight Gain: An Ambispective Cohort Study

Objective

To describe the body composition in preschool children and to evaluate the association with prepregnancy BMI and gestational weight gain (GWG).

Methods

Children were recruited in their first year in kindergarten (3 years old) and followed up for the next 2 years. Information during pregnancy and birth was retrieved from medical records. Height, weight, fat mass, fat-free mass, and percentage of body fat (FM%) were measured through a bioelectrical impedance analysis for each child visit, and BMI, fat mass index (FMI), and fat-free mass index (FFMI) were calculated. Generalized linear mixed models (GLMMs) were used to evaluate the associations between prepregnancy weight, GWG, and adiposity indicators.

Results

A total of 3,329 single-birth 3-year-old children were recruited as the baseline population and were followed at 4 and 5 years old. During the 3 years of follow-up, the mean (±SD) values of BMI, FMI, FFMI, and FM% of the children were 15.6 (±1.6) kg/m², 2.8 (±1.3) kg/m², 12.8 (±0.7) kg/m², and 17.2% (±5.8%), respectively. The prevalence rates of overweight and obesity in mothers before pregnancy were 16.6 and 3.2%, respectively. Mothers were divided into three groups based on GWG: appropriate (1,233, 37.0%), excessive (767, 23.0%), and insufficient (1,329, 39.9%). GLMMs analyses showed that the preschool children’s BMI, FMI, FFMI, and FM% were all significantly positively related to maternal prepregnancy BMI and GWG (all P < 0.001); the children of mothers who were overweight/obese before pregnancy were more likely to be overweight/obese, high FMI, high FFMI, and high FM% at preschool age (all P < 0.001); although maternal excessive GWG was not correlated with offspring’s overweight/obese (P = 0.156), the children of mothers with excessive GWG are more likely to have higher FMI, but not to be with a higher FFMI status than the children of mothers with appropriate GWG. For prepregnancy overweight/obese women, compared with the GWG-appropriate group, maternal excessive GWG was related to the risk of high FMI (coefficient = 0.388, 95% CI: 0.129–0.647) and high FM% (coefficient = 0.352, 95% CI: 0.097–0.607), but was not related to the risk of overweight/obese or high FFMI of the offspring at preschool age.

Conclusion

Fat mass index decreased with age, while FFMI increased with age among 3- to 5-year-old children. It is necessary to optimize maternal weight prior to conception and GWG management to improve the health outcomes of the offspring.

Development and validation across trimester of the Prenatal Eating Behaviors Screening tool

Rapid screening tools are useful for identifying at-risk patients and referring them for further assessment and treatment, but none exist that consider the unique medical needs of pregnant women with eating disorders (EDs). There is a need for a rapid, sensitive, and specific screening tool that can be used to identify a potential ED in pregnancy. We started with a set of 25 questions, developed from our qualitative work along with other ED screening tools, and tested on a development (n = 190) and validation sample (n = 167). Statistical analysis included factor analysis and logistic regressions with ROC curves. Development and validation samples were combined for trimester analysis (n = 357). Refining the tool to 12 items demonstrated strong internal reliability (development alpha = 0.95, validation alpha = 0.91). With correlated errors, questions demonstrated acceptable CFA fit (development: GFI: 0.91, RMSEA: 0.10, NNFI: 0.95; validation: GFI: 0.85, RMSEA: 0.14, NNFI: 0.86). Similar fits were seen by trimester: first trimester n = 127, GFI: 0.89, RMSEA: 0.12, NNFI: 0.94; second trimester n = 150, GFI: 0.83, RMSEA: 0.14, NNFI: 0.88; third trimester n = 80, GFI: 0.99, NNFI: 0.99. Validation against current ED diagnosis demonstrated acceptable sensitivity and specificity using a cutoff of 39 (development sensitivity = 80.7%, specificity = 79.7%, OR = 16.42, 95% CI: 7.51, 35.88; validation sensitivity = 69.2%, specificity = 86.5%, OR: 17.43, 95% CI: 6.46, 47.01). Findings suggest the PEBS tool can reliably and sensitively detect EDs across pregnancy trimesters with 12 questions. A further implication of this work is to reduce health and mental health treatment disparities through this standard and rapid screening measure to ensure early identification and treatment.

Reducing intergenerational obesity and diabetes risk

To address the intergenerational transmission of obesity and diabetes, strategies promoting the health of women of reproductive age appear to be urgently needed. In this narrative review, we summarise what has been learned from many prenatal clinical trials, discuss the emerging evidence from preconception clinical trials and highlight persistent gaps and critical future directions. Most trials tested prenatal interventions that resulted in a limited gestational weight gain of ~1 kg and reduced gestational diabetes by 20-30%. These interventions also reduced macrosomia by 20-40% but had little-to-no impact on other offspring outcomes at birth or beyond. Far fewer trials tested preconception interventions, with almost all designed to improve conception or live-birth rates in overweight or obese women with infertility rather than reduce intergenerational risks in diverse populations. Preconception trials have successfully reduced weight by 3-9 kg and improved markers of glucose homeostasis and insulin resistance by the end of the intervention but whether effects were sustained to conception is unclear. Very few studies have reported offspring outcomes at birth and beyond, with no evidence thus far of beneficial effects on offspring obesity or diabetes risks. Further efforts to develop effective and scalable strategies to reduce risk of obesity and diabetes before conception should be prioritised, especially for diverse and under-resourced populations at disparately high risk of obesity and diabetes. Future clinical trials should include interventions with high potential for dissemination, diverse populations, thorough maternal phenotyping from enrolment through to conception and pregnancy, and rigorous assessment of offspring obesity and diabetes risks from birth onwards, including into the third generation.