Placental ischemia and changes in umbilical and uteroplacental arterial and venous hemodynamics.
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 (greater than mean + 2 SD of the normal population) and abnormal BFC at the final antenatal examination were significantly associated with the occurrence of IUGR (birthweight less than or equal to mean - 2 SD) (p less than 0.001), operative delivery for fetal distress (p less than 0.001), and a low 1-minute Apgar score (less than or equal to 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 umbilical artery examination, which can be performed 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.