Umbilical artery Doppler velocimetry as a predictor of fetal hypoxia and acidosis at birth.

We studied the relationship between preoperative umbilical artery Doppler waveforms and umbilical vein pO2 and pH at elective cesarean section. An absence of end-diastolic velocities had a strong statistical association with hypoxia and acidosis, and was an accurate clinical test for hypoxia (sensitivity 78%, specificity 98%, positive predictive value 88%, and negative predictive value 98%) and acidosis (sensitivity 90%, specificity 92%, positive predictive value 53%, and negative predictive value 100%). It was also a clinically sensitive indicator of perinatal morbidity and mortality. Most fetuses with no end-diastolic velocities were growth-retarded, but the reverse was not true. The absence of end-diastolic velocities also divided both mature and immature fetuses into high- and low-risk groups for hypoxia and acidosis. In the presence of end-diastolic velocities, only very high S/D ratios (above 4.5) have any association with hypoxia. As a noninvasive test of fetal umbilical vein pO2 and pH, umbilical artery Doppler performs well.