Clinical usefulness of maternal body mass index in twin pregnancies

Objective: We examined whether maternal body mass index (BMI) during prepre gnancy is useful for prediction of maternal preeclampsia in twin pregnancie s. Methods: We studied 250 dichorionic twin pregnancies and 3196 singleton pre gnancies. Maternal BMI was calculated during prepregnancy in both twin and singleton pregnancies. The incidence of maternal preeclampsia was compared among three groups, low-BMI [< -1.5 standard deviations (SD)], normal-BMI, and high-BMI (> +1.5 SD) groups, in both singleton and twin pregnancies. Results: In singleton pregnancies, the incidence of maternal preeclampsia i n the high-BMI group was significantly higher than that in the normal-BMI g roup (p < 0.05). The relative risk by high BMI was 8.5 (95% confidence inte rval: 5.6-12.0). However, in twin pregnancies, no significant differences w ere observed in these values. Conclusions: Body mass index during prepregnancy was not useful for the pre diction of preeclampsia in twin pregnancies. Mechanisms other than maternal weight may be associated with the beginning of preeclampsia in twin pregna ncies.