A 30-year-old pregnant woman with a history of an uncomplicated curettage for incomplete abortion was seen at 33 weeks' gestation with decreased fetal movement and intermittent abdominal pain for 1 week. Ultrasonographic evaluation demonstrated a singleton vertex pregnancy, oligohydramnios, and a fundal uterine rent continuous with a large, fluid-filled cystic mass. Laparotomy revealed a right cornual uterine rent with hourglass amniotic sac and fluid. A healthy infant was delivered by cesarean section.