Maternal obesity in singleton versus twin gestations: a population-based matched case-control study

To examine the impact of pre-pregnancy obesity on adverse outcomes in twin compared to singleton pregnancies.

Dichorionic twin gestations with maternal body mass index >30 were matched to three singleton controls. Both obese groups were matched (1:3) with non-obese controls. Rates of preeclampsia, gestational diabetes, cesarean section, and preterm birth were compared.

One hundred eighty-nine dichorionic twin pregnancies in obese mothers were matched to 567 twin pregnancies in non-obese mothers, and to 567 singleton pregnancies in obese mothers. The latter were matched to 1701 non-obese mothers with singletons. Preeclampsia was more common in obese mothers with both twins and singletons (odds ratio (OR) 3.95, 95% confidence interval (CI) 2.18-7.16 and OR 6.53, 95% CI 3.75-11.4, respectively) as was gestational diabetes (OR 4.35, 95% CI 2.18-8.69; OR 5.53 95% CI 3.60-8.50). Obese mothers with singletons were more likely to deliver abdominally, but the cesarean rates were obesity independent in twins. Obese mothers were more likely to deliver at < 34 weeks in both twin and singleton groups (OR 1.65, 95% CI 1.10-2.48, and OR 2.41, 95% CI 1.21-4.77, respectively).

Obesity-attributable adverse outcomes are lower in twins compared to singletons. Obesity increases the risk of preterm birth regardless of plurality.