Objective: To compare 24-hour and 12-hour mifepristone-to-misoprostol intervals for second-trimester medication abortion.
Methods: We conducted a prospective randomized controlled trial. Participants were allocated to receive mifepristone either 24 hours or 12 hours before misoprostol administration. The primary outcome was the time from the first misoprostol administration to abortion (induction time). Secondary outcomes included the time from mifepristone to abortion (total abortion time); fetal expulsion percentages at 12, 24, and 48 hours after the first misoprostol dose; side effects proportion; and pain and satisfaction scores. A sample size of 40 per group (N=80) was planned to compare the 24- and 12-hour regimens.
Results: Eighty patients were enrolled between July 2020 and June 2023, with 40 patients per group. Baseline characteristics were comparable between groups. Median induction time was 9.5 hours (95% CI, 10.3-17.8 hours) and 12.5 hours (95% CI, 13.5-20.2 hours) in the 24- and 12-hour interval arms, respectively ( P =.028). Median total abortion time was 33.0 hours (95% CI, 34.2-41.9 hours) and 24.5 hours (95% CI, 25.7-32.4 hours) in the 24- and 12-hour interval groups, respectively ( P <.001). At 12 hours from misoprostol administration, 25 patients (62.5%) in the 24-hour arm and 18 patients (45.0%) in the 12-hour arm completed abortion ( P =.178). At 24 hours from misoprostol administration, 36 patients (90.0%) in the 24-hour arm and 30 patients (75.0%) in the 12-hour arm had complete abortion ( P =.139). The need for additional medication or surgical treatment for uterine evacuation, pain scores, side effects, and satisfaction levels were not different between groups.
Conclusion: A 24-hour mifepristone-to-misoprostol regimen for medication abortion in the second trimester provides a median 3-hour shorter induction time compared with the 12-hour interval. However, the median total abortion time was 8.5-hours longer in the 24-hour interval regimen. These findings can aid in shared decision making before medication abortion in the second trimester.