Primary preeclampsia in the second pregnancy: effects of changes in prepregnancy body mass index between pregnancies.

OBJECTIVE: To examine the association between changes in prepregnancy body mass index (BMI) between a woman's first two pregnancies and incidence of preeclampsia in the second pregnancy.

METHODS: We performed a population-based retrospective cohort analysis using data on women's first two singleton pregnancies (n=136,884) in Missouri (1989-1997). The study was restricted to women without preeclampsia in the first pregnancy. Prepregnancy BMI (kg/m(2)) was categorized as underweight (less than 18.5), normal (18.5-24.9), overweight (25-29.9), and obese (30 or greater). Analyses were adjusted for confounders through multivariable logistic regression.

RESULTS: The incidence rate of preeclampsia in the second pregnancy was 2.0%. In comparison with women who were of normal BMI in both pregnancies, the risk for preeclampsia increased when BMI changed between the first two pregnancies from underweight to obese (odds ratio [OR] 5.6, 95% confidence interval [CI] 1.7-18.2), normal to overweight (OR 2.0, 95% CI 1.7-2.3), normal to obese (OR 3.2, 95% CI 2.5-4.2), and overweight to obese (OR 3.7, 95% CI 3.1-4.3). Being obese or overweight in both pregnancies was associated with increased risk of preeclampsia in the second pregnancy. Women who increased their BMI from underweight to normal or overweight between pregnancies had risks of preeclampsia comparable with those with normal BMI in both pregnancies. African-American, but not white, women who had a reduction in BMI from obese or overweight to normal between pregnancies remained at increased risk for preeclampsia.

CONCLUSION: Increases in prepregnancy BMI from normal weight to overweight or obese between pregnancies are associated with increased risk of preeclampsia in the subsequent pregnancy.

LEVEL OF EVIDENCE: II.