Maternal body mass index and the risk of preeclampsia: a systematic overview.

BACKGROUND: Maternal obesity, both in itself and as part of the insulin resistance syndrome, is an important risk factor for the development of preeclampsia. Accurately quantifying the relation between prepregnancy maternal body mass index and the risk of preeclampsia may better identify those at highest risk. We performed a systematic overview of the literature to determine the association between prepregnancy body mass index and the risk of preeclampsia. METHODS: Two reviewers independently retrieved all relevant English language cohort studies through a systematic search of Medline and Embase between 1980 and June 2002. Study data were abstracted in a similar fashion. For each study, the risk ratio of preeclampsia was calculated by comparing the risk of preeclampsia among women with the highest body mass index with those with the lowest. RESULTS: We identified thirteen cohort studies, comprising nearly 1.4 million women. The risk of preeclampsia typically doubled with each 5-7 kg/m2 increase in prepregnancy body mass index. This relation persisted in studies that excluded women with chronic hypertension, diabetes mellitus or multiple gestations, or after adjustment for other confounders. CONCLUSIONS: Most observational studies demonstrate a consistently strong positive association between maternal prepregnancy body mass index and the risk of preeclampsia. Increasing obesity in developed countries is likely to increase the occurrence of preeclampsia. Consideration should be given to the potential benefits of prepregnancy weight reduction programs.