Blood Velocity Waveforms in the Fetal Aorta and Umbilical Artery as Predictors of Fetal Outcome: A Comparison

ABSTRACT

In 139 pregnancies in which intrauterine growth retardation (IUGR) was suspected at routine ultrasound screening at 32 weeks of gestation, blood velocity in the fetal aorta and umbilical artery was recorded by a pulsed Doppler ultrasound every second week until delivery. The maximum blood flow velocity waveforms (FVWs) were analyzed for pulsatility index (PI) and blood flow class (BFC). In both vessels, an abnormal PI (> mean + 2 SD of the normal population) and abnormal BFC at the final antenatal examination were significantly associated with the occurrence of IUGR (birthweight ≤ mean - 2 SD) (p < 0.001), operative delivery for fetal distress (p < 0.001), and a low 1-minute Apgar score (≤ 7). PI in the umbilical artery was a better predictor of fetal outcome than was the aortic PI, but the BFC was similarly predictive of fetal outcome in both vessels. The data indicate that a simple umbi lical artery examination, which can be preformed blindly with the Doppler ultrasound instrument without the help of a real-time scanner, is a reliable method for monitoring fetal status in pregnancies when IUGR is suspected.