Umbilical artery flow velocity waveforms in fetuses dying with congenital anomalies

Summary. Absent or reversed diastolic component in umbilical artery (UA) flow velocity waveform was observed in eight fetuses with major malformations. Because of the uncorrectable fetal conditions or the parents' reluctance to terminate the pregnancy, no interventions were undertaken and eventually all eight fetuses died in utero . The interval between the abnormal waveform recording and fetal death was between 1 and 7 days (mean 3.6 days). In two fetuses with abnormal diastolic flow, analysis of umbilical vein blood obtained by ultrasound-guided sampling revealed moderately severe acidosis and hypoxia (pH 7.228 and 7.241, Pco₂ 47.5 and 46.9 mmHg; Po₂ 14.6 and 14.7 mmHg, respectively). Our observation suggests that once the diastolic component of UA flow velocity waveforms becomes absent or reversed, the fetus is in a state of hypoxia and acidosis and fetal death is impending. This limited experience may help in formulating clinical management when using UA flow velocity waveforms in the monitoring of high-risk fetuses.