Combined impact of high body mass index and in vitro fertilization on preeclampsia risk: a hospital-based cohort study.

Abstract

Overweight and obese women may be heavy users of in vitro fertilization (IVF) owing to obesity-related oligo-anovulation. The higher doses of gonadotropins required to achieve pregnancy in obese women may contribute to impaired placentation and the development of preeclampsia. This study was designed to assess the combined effect of high maternal body mass index (BMI) and IVF on risk of preeclampsia and to evaluate for an interaction between the two factors. This is a hospital-based cohort study of 10,013 singleton pregnancies that delivered from 2001 to 2008 at a tertiary hospital in Montreal, Canada. The combined effect of high BMI and IVF on preeclampsia versus no risk factors was estimated in multivariate logistic regression models fitted with an interaction term between high BMI (> 25 or > 30 kg/m(2) ) and IVF. IVF pregnancies in obese women had a considerably higher risk of preeclampsia than spontaneous nonobese pregnancies (OR 6.7, 95% CI 3.3-13.8; p interaction 0.03). IVF was not independently associated with preeclampsia (OR 0.6, 95% CI 0.3-1.4). Analyses were similar in subgroup analyses and in analyses correcting for bias. High BMI is strongly associated with preeclampsia, and this risk is compounded in IVF pregnancies.