Reports of hyperreactio luteinalis in a spontaneously conceived pregnancy are uncommon. Hyperreactio luteinalis complicated by polyhydramnios without an identifiable cause has never been reported. The authors report a case of a 25-year-old, gravida 4, para 2-0-1-2, 16-week pregnant woman who presented with bilateral ovarian enlargement. The beta-human chorionic gonadotropin hormone was at a normal level. An exploratory laparotomy with biopsy was performed at 17 weeks of gestation. Polyhydramnios without an identifiable cause was detected at 30 weeks of gestation. A full-term healthy baby was delivered. Intrapartum and postpartum were unremarkable and both ovaries spontaneously regressed.