Continuous wave Doppler velocimetry of the main-stem uterine arteries: the transvaginal approach

The purpose of the study was (1) to establish the efficacy of the transvaginal approach for continuous wave Doppler velocimetry of the main-stem uterine arteries in normal pregnancy and (2) to provide reference values for the flow velocity waveform indices of the main-stem uterine arteries in normal pregnancy. In a cross-sectional study from 16 to 40 weeks of pregnancy, 201 healthy normal women were examined by transvaginal continuous wave Doppler, and flow velocity waveforms were obtained from the main branch of the uterine artery on both sides. Nomograms were compiled for the systolic: diastolic ratio, pulsatility index and resistance index. Values for all variables declined during the course of pregnancy until 22 weeks' gestation, and then remained stable to term. Intra- and interobserver variations were 5% and 8%, respectively, and the examination time was < 5 min. Flow velocity waveform indices declined during pregnancy, indicating a decrease of resistance in the uteroplacental circulation. Our results are comparable to those obtained transvaginally by pulsed wave Doppler, previously reported in the literature. The transvaginal approach for continuous wave Doppler velocimetry of the main-stem uterine arteries is a simple, quick, accurate, safe, cheap and highly reproducible method, and is therefore suitable for evaluating the uteroplacental circulation.