Umbilical artery flow velocity during maternal cardiopulmonary bypass.

The fetal death rate associated with cardiac operations using cardiopulmonary bypass in pregnant women is as high as 9.5% to 29%. We present a case in which fetal heart rate and umbilical artery flow velocity waveforms were continuously monitored by transvaginal ultrasonography and analyzed in relation to events of the cardiopulmonary bypass. Our findings suggest that hypothermia during cardiopulmonary bypass has potentially deleterious effects on the fetus and should be avoided if possible.