Objectives: The aim of the study was to assess the outcome of pregnancies after in vitro fertilization protocol (IVF), that were complicated by the ovarian hyperstimulation syndrome (OHSS). Material and methods: We examined 26 women undergoing IVF due to OHSS. Patients were divided into two groups: with early OHSS and late OHSS. All women were screened for age, Body Mass Index (BMI), number of embryos transferred, OHSS symptoms and duration of hospitalization. Pregnancy outcome was assessed by rate of miscarriages, premature deliveries and multiple gestations. We assessed also the delivery mode, birth weight of all newborns and obstetric complications. Results: Early OHSS occurred in 10 patients and late OHSS complicated the pregnancies of 16 women. 94,1% of the late OHSS cases occurred in cycles with pregnancy. The miscarriage rate was 26,9%. 38,5% of all births were premature and 26,9% of the newborns had low birth weight. Multiple pregnancies were confirmed in 46,2% of the patients, triplets mainly in women with late OHSS. No fetal anomalies were diagnosed. The most common antenatal complications were: diabetes mellitus, cholestasis and intrauterine infection. The rate of the cesarean sections was 73,8%. Conclusions: OHSS is a risk factor for miscarriage, preterm delivery, multiple gestation, obstetric complications and cesarean section. Late OHSS may be closely associated with the conception cycles.