Abstract
Ovarian hyperstimulation syndrome (OHSS) is a rare and occasionally fatal complication of ovulation induction. However, OHSS has occurred without interventional ovulation induction and in spontaneous ovulatory cycles. In most reported cases, physiological production of human chorionic gonadotropin was high, as in cases of multiple gestation, molar pregnancy, polycystic ovarian syndrome, and hypothyroidism. We report a very rare case of spontaneous OHSS in a healthy 36-year-old woman, gravida 5 para 2 + 2, 35 weeks pregnant, who had become pregnant naturally. According to our research, this is the first report of a case that occurred in the third trimester.