Characteristic morphology of the constricted fetal ductus arteriosus following maternal administration of indomethacin.

Indomethacin 10 mg/kg was administered to the maternal rat on the 21st day of pregnancy, and the fetal and neonatal ductus arteriosus were studied using the rapid whole-body freezing technique. The sagittal section of the frozen thorax disclosed characteristic localized constriction at the aortic end of the fetal ductus at 24 h after administration of indomethacin. Proximal dilatation of that fetal ductus persisted for more than 4 h after birth, and disappeared gradually. Shortening of the ductal length was associated with both intrauterine constriction by indomethacin in experimental rats and neonatal physiologic constriction of control rats, but significantly greater shortening was seen with intrauterine constriction.