FETAL VENOUS AND ARTERIAL FLOW VELOCITY WAVE-FORMS BETWEEN 8 AND 20 WEEKS OF GESTATION

Our purpose was to study the nature and gestational age dependency of fetal venous Doppler flow velocity wave forms and their relationship w ith fetal arterial wave forms in early pregnancy, Venous and arterial Doppler recordings were performed in 262 normal singleton pregnancies according to a cross-sectional study design at 8-20 wk of gestation. A statistically significant age-dependent increase is established for t he umbilical vein, ductus venosus, and inferior vena cava time-average d velocity. Umbilical venous pulsatile flow patterns are observed up t o 15 wk of gestation. The pulsatility index for veins in all three ven ous vessels displays a gestational age-dependent reduction. No relatio n can be established between the pulsatility index for veins and the p ulsatility index in the descending aorta and umbilical artery. This ma y be explained by the fact that the pulsatility index for veins reflec ts cardiac ventricular preload, whereas the pulsatility index in the a rterial vessels reflects down-stream impedance at fetal placental leve l.