Diet and exercise interventions during pregnancy helped women minimize excess gestational weight gain and lower the odds of caesarean section (C-section). 
Multiple clinical trials have previously demonstrated that diet, physical activity or the combination of both during pregnancy are beneficial in limiting excessive gestational weight gain. However, due to the relatively small sample sizes of these earlier trials, it remained unknown whether there were differential treatment effects in certain subgroups of women who may need additional support.
To address these evidence gaps, investigators from these individual trials established the International Weight Management in Pregnancy (i-WIP) Collaborative Group. Using the statistical technique known as Individual Patient Data (IPD) meta-analysis, they pooled individual patient data from each trial into one large study, which provided sufficient statistical power for accurate analyses. Study results were published in the peer-reviewed BMJ. 
IPD were obtained from 36 eligible randomized trials in 16 countries including Europe, North America, Australia, Brazil, Egypt and Iran and totaled 12,526 women. The IPD meta-analysis found that diet- and physical activity-based interventions resulted in less excess gestational weight gain compared with controls (no intervention), by an average of 0.7 kg (1.5 lb). Additionally, the interventions significantly reduced the odds of C-section by 9% on average.  Furthermore, the subgroup analyses found that the benefits of the interventions were similar across diverse subgroups, including baseline BMI (normal, overweight, or obese), age (≥ 20 or < 20 y/o), parity (nulliparous or multiparous), ethnicity (white or non-white), or underlying medical condition (diabetes mellitus and/or hypertension vs. none). 
This international collaboration provides access to the largest IPD in this specialty to date. However, it should be noted that the participants are predominantly white, and the ethnicity classification was limited to a binary definition: white vs. non-white. Also, the majority of the study population has a medium- to high-education status, which could be an indicator of better understanding for the need for improved lifestyle changes and result in improved compliance with interventions. These factors may limit the generalizability of the findings.
Why is this Clinically Relevant?
- Due to the obesity epidemic, half of all women of childbearing age worldwide are now overweight or obese
- Excessive weight prior to pregnancy or during pregnancy have been linked to complications for both the mother and the infant
- Clinicians should encourage and assist all women during the pre- and perinatal periods to engage in diet and physical activity, as such interventions help attenuate excessive weight gain during pregnancy and reduce C-section risk
- Clinicians should promote and help facilitate lifestyle changes including appropriate nutrition and exercise during the perinatal period
 International Weight Management in Pregnancy (i-WIP) Collaborative Group. Effect of diet and physical activity based interventions in pregnancy on gestational weight gain and pregnancy outcomes: meta-analysis of individual participant data from randomised trials. BMJ. 2017;358:j3119.