Objectives: Among many risk factors for preeclampsia (PE), prepregnancy body mass index (BMI) is one of few controllable factors. However, there is a lack of stratified analysis based on the prepregnancy BMI. This study aimed to determine the influencing factors for PE and assess the impact of PE on obstetric outcomes in twin pregnancies by prepregnancy BMI.
Methods: This was a retrospective cohort study between January 1, 2017, and December 31, 2022, in Southwest China. Impact factors and associations between PE and obstetric outcomes were analyzed separately for twin pregnancies with prepregnancy BMI < 24kg/m2 (non-overweight group) and BMI ≥ 24kg/m2 (overweight group).
Results: In total, 3602 twin pregnancies were included, of which, 672 women were allocated into the overweight group and 11.8% of them reported with PE; 2930 women were allocated into the non-overweight group, with a PE incidence of 5.6%. PE had a negative effect on birthweight and increased the incidence of neonatal intensive care unit admission in both the overweight and non-overweight groups (43.0% vs. 28.0%, p = .008; 45.7% vs. 29.1%, p < .001). Among overweight women, PE increased the proportion of postpartum hemorrhage (15.2% vs. 4.4%, p < .001). After adjustments, multivariate regression analysis showed that excessive gestational weight gain (aOR = 1.103, 95% CI: 1.056-1.152; aOR = 1.094, 95% CI: 1.064-1.126) and hypoproteinemia (aOR = 2.828, 95% CI: 1.501-5.330; aOR = 6.932, 95% CI: 4.819-9.971) were the shared risk factors for PE in both overweight and non-overweight groups. In overweight group, in vitro fertilization was the other risk factor (aOR = 2.713, 95% CI: 1.183-6.878), whereas dichorionic fertilization (aOR = 0.435, 95% CI: 0.193-0.976) and aspirin use during pregnancy (aOR = 0.456, 95% CI: 0.246-0.844) were protective factors. Additionally, anemia during pregnancy (aOR = 1.542, 95% CI: 1.090-2.180) and growth discordance in twins (aOR = 2.451, 95% CI: 1.215-4.205) were connected with an increased risk of PE only in non-overweight twin pregnancies.
Conclusions: Both discrepancy and similarity of impact factors on developing PE were found between overweight and non-overweight twin pregnancies in this study. However, the dosage and initiation time of aspirin, as well as twin chorionicity on the occurrence of PE in two subgroups, are still debated.
Keywords: Preeclampsia; obstetric outcomes; overweight; prepregnancy body mass index; twin pregnancies.