Labetalol does not alter the placental and fetal blood flow or maternal prostanoids in pre-eclampsia.

The effect of intravenously administered labetalol (1 mg/kg) on placental and fetal blood flow was studied in 13 pre-eclamptic women. Although the maternal blood pressure decreased, no changes occurred in the blood flows in the intervillous space, the umbilical vein or the fetal descending aorta, nor did the indices of peripheral vascular resistance in the fetal aorta change, but the placental vascular resistance did decrease. Labetalol had no effect on prostacyclin or thromboxane A2 as measured by urinary 6-keto-prostaglandin F1 alpha and serum thromboxane B2 respectively. These findings are clinically relevant since they suggest that labetalol reduces maternal blood pressure without interfering with the placental or fetal blood flow.