Cerebral Doppler ultrasound of the human fetus.

Maximal flow velocity waveforms were recorded in the internal carotid artery (ICA), middle cerebral artery (MCA), posterior cerebral artery (PCA) and anterior cerebral artery (ACA) in 55 normal pregnancies and 14 complicated by intrauterine growth retardation between 25 and 41 weeks gestation. In normal pregnancy, acceptable flow velocity waveforms were obtained in the ICA in 89%, in the MCA in 91%, in the PCA in 58% and in the ACA in 64%. A decrease in pulsatility was observed in all four intracranial arteries during the latter weeks of gestation. In growth-retarded pregnancies, pulsatility in all vessels was significantly reduced compared with normal pregnancy, suggesting participation of all major intracranial arteries in a brain-sparing effect in the presence of chronic fetal hypoxia.