For chronic fetal hypoxia due to maternal Ebstein’s anomaly, oxygen was administered daily to the mother by mask for 105 days. At 20 weeks of gestation, umbilical venous blood gases in room air showed pH 7.42, PO2 25.7 mm Hg, PCO2 33.7 mm Hg and O2 saturation 48.7%, and changed to 7.45, 39.1 mm Hg, 25.9 mm Hg and 77.4% on 3 liters/min of oxygen inhalation by mask, respectively. The PO2 of the maternal arterial blood gases increased to 30 mm Hg on oxygen administration at 15 weeks of gestation, but at 25 weeks of gestation the PO2 increased by only about 10 mm Hg. At 30 weeks, intrauterine growth retardation was suspected. Just after the second puncture of the umbilical cord at 31 weeks and 3 days of gestation, 80 bpm fetal bradycardia occurred for several minutes without recovery and emergency cesarean section was done under the general anesthesi