The effect of nifedipine therapy on fetal and placental Doppler waveforms in preeclampsia remote from term.
 Twenty patients with preeclampsia at a gestational age of 26 to 35 weeks were treated with oral nifedipine until delivery.
 The mean oral daily dose was 45.1 +/- 11 mg/day (range, 40 to 80 mg/day).
 Fetal aorta, internal carotid artery, umbilical artery, and uteroplacental Doppler flow velocity waveforms were recorded before treatment and then serially.
 The mean nifedipine concentration at the time of the Doppler studies was 60.3 ng/ml (range, 10 to 90 ng/ml).
 The use of nifedipine therapy was associated with a significant decrease in both maternal systolic blood pressure (baseline, 154 to 135 mm Hg, p less than 0.001) and diastolic blood pressure (baseline, 100 to 88 mm Hg, p less than 0.001).
 However, there was no significant difference in the resistance index between baseline and postnifedipine Doppler studies in either the fetal or uteroplacental vessels.
 The use of oral nifedipine to control blood pressure in preeclampsia does not affect the resistance indices in fetal or uteroplacental vessels as measured by the Doppler technique.
