Journal of Ultrasound in Medicine, Vol 10, Issue 6 301-304, Copyright © 1991 by American Institute of Ultrasound in Medicine
Effect of calcium channel blocker nifedipine on uterine artery flow velocity waveforms
I. Thaler, Z. Wiener, D. Manor and J. Itskovitz
Department of Obstetrics and Gynecology, Rambam Medical Center, Haifa, Israel.
Calcium channel blockers have been used successfully in the treatment of
pregnancy hypertension and premature labor. Only limited information
related to their effect on uterine blood flow during pregnancy is
available. In this study we measured the ratio between peak systolic to
end-diastolic flow velocity (S/D ratio) in the ascending branch of the
uterine artery in nine pregnant patients prior to and following a 10-mg
dose of sublingual nifedipine. Another group of seven matched patients who
received a placebo served as a control group. All studies were performed
between 17 and 22 weeks gestation. The S/D ratio decreased shortly after
sublingual nifedipine, but the change was not significant. It increased
gradually afterward so that by 60 minutes it returned to the control value.
The mean systolic blood pressure decreased by 8.6% to its lowest value
after 25 minutes (P less than 0.01). The mean diastolic blood pressure
decreased by 15.7% to its lowest value after 35 minutes (P less than
0.002). Maternal heart rate did not change significantly. No significant
changes were observed in any of the measured variables in the placebo
group. In conclusion, nifedipine does not induce significant changes in
uterine arterial resistance in midtrimester and may be considered during
pregnancy, providing that large fluctuations in maternal blood pressure are
avoided.
