AbstractTransvaginal color Doppler was performed in 198 volunteer pregnant women whose menstrual age ranged from the fifth to the twelfth week. In all patients an attempt was made to obtain signals from both uterine arteries, peritrophoblastic/retroplacental vessels, umbilical arteries, fetal aorta, intracranial vessels, and corpus luteum flow.With the combination of color and pulsed Doppler transvaginal sonography, detection of vascular structures was greatly facilitated and the amount of time for examination significantly reduced. Flow velocity waveforms were measured and results were analyzed by calculation of the Resistance Index.During the early stage of pregnancy, we were able to locate both uterine arteries in all cases and continuous diastolic shift signal was found. Flow in the peritrophoblastic/retroplacental area was observed with an overall success rate of 94%. Blood flow in the umbilical artery and fetal aorta was visualized by color Doppler starting from the seventh week. Intracranial blood flow could be visualized starting from the tenth week in some cases. Diastolic flow in these vessels was detectable starting from the twelfth week. Corpus luteum flow was found in 148 cases (75%) and the Resistance Index decreased as pregnancy progressed © 1993 by John Wiley&Sons, Inc