Reverse end-diastolic flow in the middle cerebral artery: an agonal pattern in the human fetus.

Serial Doppler ultrasonography in a severely growth-restricted fetus revealed progressive reduction in pulsatility index of the middle cerebral artery, consistent with brain-sparing effect. At 29 weeks, 1 week before fetal death, the pulsatility index in the middle cerebral artery returned to normal values and became reversed the day before fetal death. This report suggests that reverse flow in the middle cerebral artery is one of the terminal hemodynamic events preceding fetal death.