Pulsed wave Doppler curves of fetal vessels. With progressing deterioration (encoded with background colors) significant changes in the end-diastolic phase of the velocity wave forms of the fetal vessels are recorded. In the umbilical artery (UA), increasing placental resistance causes progressively decreasing end-diastolic velocities, with zero or reverse flow in most advanced stages. In the middle cerebral artery (MCA), decreasing vascular resistance owing to dilation of cerebral vessels…