Studies on closure of the ductus arteriosus. XI. Ductal closure by a prostaglandin synthetase inhibitor

Intrauterine contraction of the ductus arteriosus in fetuses followed a single oral dose of 15 mg/kg indomethacin to pregnant rats 12 or 18 h prior to delivery. This ductal contraction studied by the whole-body freezing technique was markedly pronounced up to 30 min after delivery. Blood gas measurements showed a low pH at 30 min which returned to normal at 120 min. Cyanosis was persistant in the indomethacin groups. Intrauterine ductal closure may be a danger to the fetus and subsequent postnatal adjustment. The present results need confirmation in other species to predict a similar risk in the human fetus.