Nifedipine: Effects on fetal and maternal hemodynamics in pregnant sheep

We investigated the effects of nifedipine, a calcium entry blocker, on the fetal and maternal circulation. Nifedipine was administered intravenously for 30 minutes to chronically instrumented pregnant ewes. Infusion of 5 µg·kg⁻¹ ·kg min⁻¹ resulted in a 30% to 50% increase in total and regional fetal cerebral blood flow to the brain stem, watershed, and subcortical regions (p < 0.05), without a significant change in fetal oxygenation or cardiac output. Infusion of 10 µgkg·kg⁻¹·kg·min⁻¹ decreased uterine blood flow by 21 (p < 0.001) and fetal arterial oxygen content by 15% (p < 0.01), with no further increase in fetal cerebral blood flow. Maternal arterial pressure decreased and heart rate increased (p < 0.001) without variation of arterial blood gases. Significant plasma levels of nifedipine were detected in the fetal and maternal circulations. In view of the potential adverse effects on the fetus, further studies are needed before nifedipine is considered for use in human pregnancy.