Prenatal detection of intrauterine closure of the ductus arteriosus unrelated to maternal administration of non-steroidal anti-inflammatory drugs or glucocorticoids made it possible to study the circulation in this condition in the human fetus and newborn by pre- and postnatal echocardiography and neonatal cardiac catheterization. At 38 weeks, the fetus presented intrauterine ductal closure associated with right ventricular dilatation and marked hypertrophy of the right ventricle and the interventricular septum, as well as severely diminished right ventricular fractional shortening and diminished pulmonary blood flow. Blood flow redistribution was characterized by reduced blood flow through the right heart and increased right-to-left shunting across the dilated foramen ovale. Pathological Doppler waveforms of the inferior vena cava and the ductus venosus were found, although the cardiotocogram was normal. Following unsuccessful induction of labour a Caesarean section was performed. Postnatal echocardiography confirmed the prenatal findings. Cardiac catheterization, performed because of persistent dependence on additional oxygen administration, revealed increased pulmonary vascular resistance, reduced pulmonary blood flow, and prolonged right-to-left shunt across the foramen ovale. Reduced peripheral pulmonary artery diameters were shown angiographically. Follow-up examinations revealed regression of right ventricular hypertrophy and recovery of right ventricular and pulmonary function. The findings confirm results from haemodynamic studies in animal experiments.