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

OBJECTIVE To assess the separate and combined associations of maternal pre- pregnancyBMI and gestational weight gainwith the risks of pregnancycomplications and their population impact. DESIGN Individual participant datameta-analysis of 39 cohorts. SETTING Europe, North America and Oceania. POPULATION 265,270 births. METHODS Information on maternal pre- pregnancyBMI, gestational weight gain, and pregnancycomplications was obtained. Multilevel binary logistic regression models were used. MAIN OUTCOME MEASURES Gestational hypertension, pre-eclampsia, gestational diabetes, preterm birth, small and large size for gestationalage at birth. RESULTS Higher maternal pre- pregnancyBMI and gestational weight gainwere, across their full ranges, associated with higher risks of gestational hypertensivedisorders, gestational diabetesand large size for gestationalage at birth. Preterm birth risk was higher at lower and higher BMI and weight gain. Compared to normal weight mothers with medium gestational weight gain, obese mothers with high gestational weight gainhad the highest risk of any pregnancycomplication (Odds Ratio 2.51 (95% Confidence Interval 2.31, 2.74)). We estimated that 23.9% of any pregnancycomplication was attributable to maternal overweight/obesity and 31.6% of large size for gestationalage infants was attributable to excessive gestational weight gain. CONCLUSIONS Maternal pre- pregnancyBMI and gestational weight gainare, across their full ranges, associated with the risks of pregnancycomplications. Obese mothers with high gestational weight gainare at the highest risk of pregnancycomplications. Promoting a healthy pre- pregnancyBMI and gestational weight gainmay reduce the burden of pregnancycomplications and ultimately the risk of maternal and neonatal morbidity. This article is protected by copyright. All rights reserved.