In utero isolated ductal closure is uncommon and can lead to fetal hydrops and death if not recognized. Five fetuses were diagnosed prenatally by echocardiography. The reasons for referral were hydrops (2), cardiomegaly (1), polyhydramnios and choroid plexus cyst (1), and polyhydramnios and teratoma of the neck (1). Gestational age was median 32, range 18-41 weeks. Two mothers received indomethacin for polyhydramnios, with the echocardiogram performed 5 and 3 days after the last dose. Three had a negative history of drug ingestion. Fetal echocardiograms showed absent flow in the ductus arteriosus, dilated right ventricle with decreased function, and mild or moderate tricuspid and pulmonary insufficiency in all. The left ventricle was hypercontractile, with significantly increased left ventricular stroke output when compared to the right. Four fetuses were delivered by cesarean section and had an uneventful course. One fetus died shortly after birth due to airway obstruction from a large teratoma. Autopsy showed ductal constriction. Postnatal echocardiograms showed absent ductal flow and dilated right ventricle. On follow-up, survivors remained asymptomatic with cardiac size returning to normal. Premature closure of the ductus arteriosus should be considered in hydrops of unknown etiology, right ventricular dysfunction, and following indomethacin therapy. Urgent delivery results in an excellent prognosis.