The effect of magnesium sulfate on maternal and fetal blood flow in pregnancy-induced hypertension.

The purpose of this study was to evaluate the effects of magnesium sulfate on maternal and fetal blood flow in pregnancy-induced hypertension. Twelve patients with pregnancy-induced hypertension were prospectively studied with transcranial pulsed Doppler and transabdominal color flow Doppler before and after infusion of a 6 gram intravenous loading dose of magnesium sulfate. The maternal vessels studied included the middle cerebral, common carotid, and internal carotid arteries. The fetal vessels studied included the middle cerebral, renal, and umbilical arteries. In addition the maternal circulation in the placental base plate was imaged. The results of this descriptive study suggest that a 6 gram loading dose of magnesium sulfate significantly vasodilates the vascular bed distal to the maternal middle cerebral artery, and increases blood velocity in this distribution. There was no significant change in pulsatility index or blood velocity in the central large vessels of the head and neck. There were no acute effects noted in the fetal or placental vessels evaluated.