Doppler velocimetry measured in retrochorionic space and uterine arteries during early human pregnancy

The natural course of uterochorionic vascular resistance during the first trimester of pregnancy is described. We performed a weekly study using a pulsed Doppler in 25 normal pregnancies, with a total of 191 examinations made. The flow velocity waveform was studied simultaneously in the retrochorionic area as well as in the uterine arteries. Different velocimetry indices were analysed, which demonstrated the feasibility of the (D/S) x 100 index for study of the retrochorionic vessels and of the Pourcelot index (S-D/S) for the uterine arteries. A gradual weekly decrease in flow resistance was found, with significant differences before [(D/S) x 100 = 52.01 +/- 8.33; S-D/S = 0.83 +/- 0.09] vs after the 9th week [(D/S) x 100 = 58.9 +/- 8.78; S-D/S = 0.72 +/- 0.10]. Further evaluation of its predictive and diagnostic value in gestational pathology is necessary.