Degree of obesity at delivery and risk of preeclampsia with severe features

Background The risk of preeclampsia increases as maternal body mass index (BMI) increases. The link between increasing maternal BMI and preeclampsia with severe features is less well-established. Objective To estimate the effect of increasing severity of obesity on risk of preeclampsia with severe features, stratified by early-onset and late-onset disease. Study Design We performed a retrospective cohort study of consecutive singleton live births at a tertiary care facility from 2004 to 2008. Women were included in the cohort if they delivered a singleton live birth and maternal height and weight was measured on admission. The primary exposure was maternal weight category on presentation for delivery, defined as normal (BMI 18.5-24.9; referent group, n = 1473), overweight (BMI 25-29.9, n = 3081), obese (BMI 30-39.9, n = 4196), and morbidly obese (BMI ≥40, n = 1446). The primary outcome was preeclampsia with severe features. Secondary outcome was early-onset preeclampsia with severe features at <34 weeks or late-onset preeclampsia with severe features at ≥34 weeks. Multivariable logistic regression was used to adjust for confounders. Results Of the 10,196 patients meeting inclusion criteria, 1119 developed preeclampsia. Of those, 881 (8.6%) women developed preeclampsia with severe features. Overall, the risk of preeclampsia with severe features was not significantly different in the 4 BMI categories. Of the 10,196 women in the cohort, 1072 delivered <34 weeks and 9124 delivered ≥34 weeks. When stratifying by gestational age at delivery, there was a statistically significant increased risk of developing late-onset preeclampsia with severe features at ≥34 weeks in overweight (4.5%, adjusted odds ratio [aOR] 1.4, 95% confidence interval [CI] 1.0-2.1), obese (6.2%, aOR 2.0, 95% CI 1.4-2.8) and morbidly obese (6.8%, aOR 2.0, 95% CI 1.3-2.9) women compared with normal-weight women (2.9%). Conclusion Increasing maternal weight was not associated with preeclampsia with severe features in the total cohort; however, overweight, obese, and morbidly obese women are at increased risk of developing late-onset preeclampsia with severe features.