- To identify maternal factors that increase the risk of preeclampsia in twin gestations and to investigate whether twins conceived by in vitro fertilization (IVF) lead to an increased risk of preeclampsia development. A retrospective population-based cohort study of twin deliveries was performed. Maternal characteristics and perinatal outcomes were evaluated. Patients' data were obtained from a computerized database and analyzed using SPSS statistical package. During the study period there were 2628 twin deliveries, and of these 3.1% had severe preeclampsia and 6.16% mild preeclampsia. Patients with severe preeclampsia were more likely to be primiparous, and to have significantly higher frequency of chronic hypertension, gestational diabetes mellitus (GDM), IVF treatments, cesarean delivery, preterm delivery and twin discordancy than in the normotensive patients. Chronic hypertension, pirimiparity, twin discordancy and maternal age were independent risk factors for the development of preeclampsia. In a multivariate regression model including IVF treatment, parity and maternal age as risk factors for preeclampsia, women younger than 35 years that conceived following IVF treatments had an independent risk factor for the development of preeclampsia. IVF treatments in primiparous patients and age younger than 35 years are independent risk factors for preeclampsia. Twin discordancy is an additional independent risk factor for the occurrence of preeclampsia.