Acute Effect of Dihydralazine on Uteroplacental Blood Flow in Hypertension during Pregnancy

The uteroplacental blood flow was measured in 12 women with hypertension during pregnancy before and after intravenous injection of dihydralazine. After intravenous administration of 18.5 MBq (0.5 mCi) 113mIn, the gamma radiation emanating from the placenta was recorded with a computer-linked gamma camera during 10-second intervals for 240 s. From time-activity analysis of the isotope curve a uteroplacental blood flow index could be calculated. 30 min after the intravenous injection of dihydralazine, 18.5 MBq 113mIn were again administered, and a second uteroplacental blood flow index was calculated. After dihydralazine administration there was a significant reduction of mean blood pressure (p less than 0.01) and an increase of mean maternal heart rate (p less than 0.01). There was no significant change in uteroplacental blood flow or in uteroplacental vascular resistance.