Umbilical artery pulsatility index and half-peak systolic velocity in second- and third-trimester fetuses with trisomy 18 and 13.

A high prevalence of abnormal UA Doppler velocimetry was found in second- and third-trimester fetuses with trisomy 18 and 13, which further increased with gestational age. These results may well correlate with alterations described previously in the placenta, suggesting placental insufficiency has an important role in the development of FGR in these autosomal aneuploid fetuses.