Evacuation interval after vaginal misoprostol for preabortion cervical priming: a randomized trial.

OBJECTIVE: To determine the optimal interval for evacuation after preabortion cervical priming with vaginal misoprostol. METHODS: One hundred eighty healthy nulliparas requesting legal termination of pregnancy between 6 and 11 weeks' gestation were assigned randomly to receive 400, 600, or 800 microg of intravaginal misoprostol. Vacuum aspiration was done after 3 hours in the 400-microg group and after 2 hours in the 600- and 800-microg groups. The degree of cervical dilatation before operation was measured with a Hegar dilator. Preoperative and intraoperative blood loss and associated side effects were also assessed. RESULTS: Eleven (18.3%) and 15 (25.0%) women in the 600-and 800-microg groups, respectively, had cervical dilatation of at least 8 mm after an interval of 2 hours; 55 (91.7%) women who received 400 microg for a 3-hour interval had similar cervical dilatation. Using 400 microg as a baseline, the odds ratio (OR) was 0.02; 95% confidence interval (CI) was 0.01, 0.06 for 600 microg and OR 0.03; 95% CI 0.01, 0.09 for 800 microg for achieving successful preabortion cervical dilatation of at least 8 mm. The mean cervical dilatation of 6.7 mm and 6.8 mm for the higher doses was also significantly less than that of 8.1 for the 400-microg dose (P<.001). The mean preoperative and intraoperative blood loss was only statistically different when the 400- and 800-microg groups were compared (P = .03). There were also significantly more side effects, namely abdominal pain and fever above 38.0 C, in the 600- and 800-microg groups (P<.001), compared with the 400-microg group. When the 600- and 800-microg groups were compared, there were still significantly more women complaining of abdominal pain (P<.001). None of the women in the study required analgesics for pain or antipyretics for fever. CONCLUSION: The minimal evacuation interval should be at least 3 hours for successful preabortion cervical priming.