Blood flow velocity waveforms in human fetal intracranial arteries.

Blood flow velocity waveforms were recorded by pulsed Doppler examination from fetal intracranial arteries in 83 normal and 84 high-risk pregnancies. The normal cases showed a decreasing resistance index of the waveform toward the end of pregnancy, and a continuous forward flow that was always present in these arteries. A low resistance index predicted the birth of a small-for-dates newborn and/or the appearance of subsequent cardiotocographic abnormality, with 57% sensitivity and 94% specificity. Two hydrocephalic fetuses had abnormally high resistance index values. An abnormal fetal intracranial arterial velocity waveform can be seen as a sign of increased perinatal risk.