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
\nTo assess the separate and combined associations of maternal pre-pregnancy BMI and gestational weight gain with the risks of pregnancy complications and their population impact.
\nDESIGN
\nIndividual participant data meta-analysis of 39 cohorts.
\nSETTING
\nEurope, North America and Oceania.
\nPOPULATION
\n265,270 births.
\nMETHODS
\nInformation on maternal pre-pregnancy BMI, gestational weight gain, and pregnancy complications was obtained. Multilevel binary logistic regression models were used.
\nMAIN OUTCOME MEASURES
\nGestational hypertension, pre-eclampsia, gestational diabetes, preterm birth, small and large size for gestational age at birth.
\nRESULTS
\nHigher maternal pre-pregnancy BMI and gestational weight gain were, across their full ranges, associated with higher risks of gestational hypertensive disorders, gestational diabetes and large size for gestational age 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 gain had the highest risk of any pregnancy complication (Odds Ratio 2.51 (95% Confidence Interval 2.31, 2.74)). We estimated that 23.9% of any pregnancy complication was attributable to maternal overweight/obesity and 31.6% of large size for gestational age infants was attributable to excessive gestational weight gain.
\nCONCLUSIONS
\nMaternal pre-pregnancy BMI and gestational weight gain are, across their full ranges, associated with the risks of pregnancy complications. Obese mothers with high gestational weight gain are at the highest risk of pregnancy complications. Promoting a healthy pre-pregnancy BMI and gestational weight gain may reduce the burden of pregnancy complications and ultimately the risk of maternal and neonatal morbidity. This article is protected by copyright. All rights reserved.