Misoprostol's effect on uterine arterial blood flow and fetal heart rate in early pregnancy.

OBJECTIVE

To determine whether a single oral dose of misoprostol is associated with change in Doppler resistance indices (RIs) of the uterine artery in early pregnancy.

METHODS

Forty pregnant women seeking legal termination of pregnancy at 7-15 completed gestational weeks were each given a single oral dose of 200 microg misoprostol. Resistance indices (A/B ratio) and pulsatility index (PI) of the uterine arteries (UA) and fetal heart rate (FHR) were assessed by Doppler ultrasound before and 1 hour after administration of misoprostol.

RESULTS

Doppler RIs (UA-A/B and UA-PI) of the right and left uterine arteries increased significantly 1 hour after misoprostol administration. The right UA-A/B increased from 7.16 +/- 1.09 (mean +/- SEM) to 10.26 +/- 0.67 (P < .001), and the left UA-A/B increased from 7.40 +/- 0.72 to 9.21 +/- 0.82 (P = .04). The right UA-PI increased from 2.38 +/- 0.11 to 2.90 +/- 0.12 (P < .001), and the left UA-PI increased from 2.38 +/- 0.17 to 2.70 +/- 0.18 (P = .03). No significant changes in FHR were noted 1 hour after misoprostol administration. None of the fetuses died during that time.

CONCLUSION

Doppler RIs of the uterine arteries increased significantly after single oral doses of misoprostol during the first trimester, implying a reduction in arterial blood flow. Those changes were not associated with fetal death, possibly explaining congenital abnormalities associated with misoprostol in early pregnancy.