Ductus-dependent fetal cardiac defects contraindicate indomethacin tocolysis.

: The hemodynamics of critical aortic stenosis in the fetus make it a ductus-dependent cardiac defect because the ductus arteriosus supplies blood not only to the descending aorta but also to the aortic arch and coronary vessels. In utero closure of the ductus arteriosus has been reported in association with tetralogy of Fallot, truncus arteriosus, maternal use of prostaglandin inhibitors, and as idiopathic events. This is the first report of a ductus-dependent congenital heart defect (critical aortic stenosis) where treatment with indomethacin, a prostaglandin synthetase inhibitor, precipitated premature closure of the ductus and hydrops fetalis. Review of reported cases of premature closure of the ductus show that acute, in utero closure of the ductus in a fetus with limited cardiopulmonary reserves has a worse prognosis than with previously reported cardiac anomalies. This study strongly supports published concerns of increased perinatal morbidity and mortality when fetuses are exposed to prostaglandin inhibitors in utero, and shows that ductus-dependent fetal cardiac defects are contraindications to the maternal use of prostaglandin inhibitors during pregnancy.