TRANSVAGINAL COLOR DOPPLER IN THE ASSESSMENT OF PLACENTAL BLOOD-FLOW

A cross-sectional transvaginal color and pulsed Doppler study was perf ormed on 95 normal singleton pregnancies to establish blood flow chara cteristics of maternal and placental components of circulation. During the pregnancy, vascular impedance to blood flow decreases from the ma in uterine artery to the spiral arteries in the maternal component of uteroplacental circulation. In the placental component of circulation, vascular impedance decreases from the umbilical artery to the fetal a rteries within placenta-intraplacental arterioles. At the same time, i n both components of uteroplacental circulation, an increase of blood flow velocity with gestational aging was observed. There was no signif icant drop of vascular impedance of blood flow or increase of blood fl ow velocity around the 12th or 14th gestational week, which should pro ve the hypothesis of 'opening' of spiral arteries which have tips plug ged with trophoblast tissue.