Prepregnancy body mass index and gestational weight gain as risk factors for preeclampsia and transient hypertension

PURPOSE: Recent studies suggest prepregnancy obesity is a risk factor for preeclampsia, although only a handful of studies have examined the effect of gestational weight gain. The authors analyzed the effect of prepregnancy body mass index (BMI) and weight gain during pregnancy on risk of preeclampsia and transient hypertension. METHODS: Subjects were participants in a prospective cohort study of women who received prenatal care from thirteen obstetric practices in southern Connecticut (4/88–12/91). The women were interviewed in-person before 16 weeks gestation and in the immediate postpartum period. All subjectsʹ hospital delivery charts were abstracted. BMI was categorized as: <19.8 (underweight), 19.8–26 (normal: referent), 26–29 (overweight), >29 (obese). A gestational weight gain index, created using multiple linear regression, compared observed weight gain to the weight gain expected after adjustment for significant covariables (e.g. gestational aged at delivery). Logistic regression was used to estimate risk of preeclampsia (N = 44) and transient hypertension (N = 172) associated with prepregnancy BMI and gestational weight gain. RESULTS: Obese women had a mild increased risk of preeclampsia (OR = 1.81; 0.73–4.52); women in the other BMI categories had risks similar to that of normal BMI subjects. In contrast, risk of transient hypertension was substantially decreased among underweight women (OR = 0.35; 0.14–0.87) and substantially increased among obese women (OR = 3.43; 2.27–5.21). Higher than expected gestational weight gain did not increase the risk of preeclampsia. In contrast, risk of transient hypertension was increased over twofold among women in the highest quartile of the weight gain index (OR = 2.55; 1.66–3.92). CONCLUSIONS: Obesity appears to be a strong risk factor for transient hypertension and a milder risk factor for preeclampsia. High gestational weight gain was associated with increased risk of transient hypertension but not preeclampsia.