The impact of change in pregnancy body mass index on the development of gestational hypertensive disorders

OBJECTIVE: To examine the impact of change in body mass index (BMI) during pregnancy on the incidence of gestational hypertension/preeclampsia. STUDY DESIGN: This is a retrospective cohort study using linked California birth certificate and discharge diagnosis data from the year 2007. Adjusted odds ratios (aOR) and 95% confidence intervals (CI) were calculated for the outcome of gestational hypertension/preeclampsia, as a function of a categorical change in pregnancy BMI: BMI loss (<-0.5), no change (-0.5 to 0.5), minimal (0.6 to 5), moderate (5.1 to 10) and excessive (>10). The impact of change in pregnancy BMI was evaluated for the entire cohort and then as a function of prepregnancy BMI category. Women with no change in pregnancy BMI served as the reference group. RESULT: The study population consisted of 436 414 women with singleton gestations. Overall, women with excessive BMI change had a nearly twofold increased odds of gestational hypertension/preeclampsia (aOR = 1.94; 95% CI = 1.72 to 2.20). By prepregnancy BMI class, overweight and obese women who had a moderate change in pregnancy BMI also had increased odds of developing gestational hypertension/preeclampsia with aOR ranging from 1.73 to 1.97. CONCLUSION: Regardless of prepregnancy BMI category, women with excessive BMI change have a higher chance of developing gestational hypertension/preeclampsia. Overweight and obese women with moderate BMI change may also be at increased risk.