Oligohydramnios and fetal cerebral blood flow.

Blood flow velocity waveforms in the fetal internal carotid artery were recorded in five pregnancies complicated by prolonged severe oligohydramnios due to bilateral renal agenesis. End-diastolic flow velocity was reduced, absent or even reversed, resulting in a raised pulsatility index in all five cases. These data suggest that prolonged severe oligohydramnios may hamper cerebral blood flow through fetal head compression.