Uterine bloodflow velocity waveforms before and after transcervical chorionic villus sampling.

Flow velocity waveforms from the left and right uterine artery were studied relative to transcervical chorionic villus sampling (CVS) between 9 and 11 weeks of gestation in 12 uncomplicated pregnancies and 5 pregnancies resulting in second trimester fetal loss. There was no significant difference in mean pulsatility index (PI) as a measure of downstream impedance, between the left and right uterine artery. There were also no significant changes in PI relative to the CVS procedure both in uncomplicated pregnancies and in pregnancies ending in second trimester fetal loss.