(982) Comparative effectiveness of low- vs. standard-dose misoprostol for medication abortion from 24–27 weeks' gestation

Objective:
Recent guidelines on medication abortion (MAb) from 14 0/7 to 27 0/7 weeks’ gestation recommend reduced misoprostol dosing from 400mcg q3h to 200mcg q3h for cases ≥24 0/7 weeks, though data are limited as few studies include patients beyond 24 weeks. We sought to assess time to delivery and safety of misoprostol 200mcg q3h vs. 400mcg q3h for MAb from 24–27 weeks’ gestation.

Study Design:
This was a retrospective cohort study of MAbs from 24 0/7 to 27 0/7 weeks’ gestation at an urban quaternary care health network from 7/2022 to 6/2025. All patients received 2mg intraamniotic digoxin and 200mg oral mifepristone followed at 24–48 hours by buccal or vaginal misoprostol, either 200mcg q3h or 400mcg q3h. The 400mcg group included some patients who received an 800mcg misoprostol loading dose at start of induction. The primary outcome was time from first misoprostol dose to delivery. Secondary outcomes were delivery complications. We calculated descriptive statistics and performed regression analyses to estimate odds ratios with corresponding 95% CIs.

Results:
Of 55 patients, 27 received 200mcg q3h and 28 received 400mcg q3h, with demographics balanced between groups [table 1]. Mean time to delivery was 2.6 hours longer in the 200mcg group than the 400mcg group [table 2]. Receiving an 800mcg loading dose was not associated with shorter time to delivery. Receiving 200mcg q3h was associated with lower risk of fever (14.8% vs 25.0%, OR 0.52) but higher risk of retained placenta (14.8% vs 3.6%, OR 4.17) compared to 400mcg q3h. Receiving 200mcg was also associated with increased risk for estimated blood loss ≥500mL, manual placental removal, and dilation and curettage.

Conclusion:
The results of this exploratory study signal that reducing misoprostol from 400mcg q3h to 200mcg q3h for MAb from 24–27 weeks’ gestation may be associated with longer time to delivery, higher rates of retained placenta, and higher blood loss, but lower rates of fever. Larger cohorts are needed to corroborate our findings and clarify the potential benefits of reduced misoprostol dosing for MAb from 24 0/7 to 27 0/7 weeks’ gestation.