Pre-pregnancy maternal obesity and the risk of preterm preeclampsia in the American primigravida

ObjectiveTo estimate the risk of preterm preeclampsia in primiparous women by pre-pregnancy obesity class. MethodsA retrospective cohort study of primiparous women with singleton gestations was performed for deliveries from January 2003 to April 2014. Cases were stratified by delivery occurring either at37 weeks or<37 weeks. Pre-pregnancy maternal obesity was defined as a body mass index (BMI)30 kg/m(2). World Health Organization criteria were used to define BMI class of obesity. Multinomial logistic regression modeling estimated the association between term and preterm preeclampsia and pre-pregnancy obesity. ResultsOf 28,361 women with complete pre-pregnancy BMI data, 2,588 women (9.1%) had a diagnosis of preeclampsia. Women who developed preeclampsia prior to 37 weeks (n=784) were more likely to be women with obesity compared to women who developed preeclampsia after 37 weeks (33.1% vs. 25.3%, P=0.0001). Compared to normal-weight women without preeclampsia, the risk of preterm preeclampsia increased proportionally with pre-pregnancy obesity class, with women with a BMI40 kg/m(2) having the greatest risk (RR 5.23, 95% CI: 3.86-7.09, P <0.001). ConclusionsThe risk of preterm preeclampsia increased significantly as the severity of maternal pre-pregnancy obesity increased. Reduction in maternal pre-pregnancy BMI may be protective in mitigating such risk.