Abstract
Pulsed Doppler ultrasound was used to investigate human umbilical artery blood flow patterns in three fetuses where cardiac arrythymias were present, viz., congenital bradycardia, multiple extrasystoles and 'dropped beats'. The impedance to blood flow along these arteries was assessed by the pulsatility index. The results suggest that the placental vascular bed on the fetal side has a high compliance.