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CME Credit Offered
CME Credit Offered
Abstract Award
Abstract Award
Recording available 2/16-5/2
Recording available 2/16-5/2
AIUM Credit
AIUM Credit
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Foundation Awardee
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Abstract Award
Abstract Award
Foundation Awardee
Foundation Awardee

Poster Session 3

Category: Clinical Obstetrics

Poster Session 3

(833) Simultaneous Mifepristone and Misoprostol versus Misoprostol Alone in Second Trimester (MIST): A Randomized Controlled Trial

Thursday, February 12, 2026
10:30 AM - 12:00 PM  
Objective:
Mifepristone pretreatment shortens induction time and reduces retained placenta in nonviable second-trimester pregnancies. However, the required 24-to-48-hour delay may be impractical due to urgency, travel barriers, or limited access to specialized care. The MIST trial evaluated whether simultaneous mifepristone and misoprostol (mife+miso) shortens time to delivery versus misoprostol alone (miso).

Study Design:

We conducted a randomized controlled trial of patients needing urgent induction between 14w0d–27w6d. Participants were randomized 1:1 to mife+miso or miso. The primary outcome was placental delivery within 12 hours. Secondary outcomes included delivery within 18 and 24 hours, use of additional medications/instruments, obstetric morbidity, and time to delivery using Kaplan-Meier curves and Cox proportional hazard ratios. Analyses followed an intention-to-treat approach. A sample of 30 participants provided 80% power to detect an increase in 12-hour delivery from 34% to 82% with an α of 0.05.

Results:
Of 30 patients randomized, one in the miso group was withdrawn (15 mife+miso vs 14 miso in analysis). Baseline demographics, including gestational duration, parity, indication for care, and cervical dilation before induction were similar between groups. Simultaneous mifepristone use did not increase rate of delivery within 12 hours (33.3% mife+miso vs 35.7% miso, p=0.89). Delivery within 18 and 24 hours were also similar, with most patients delivering within 18 hours. Overall time to delivery was also not altered by mifepristone (fetal HR 1.67 [95% CI 0.75-3.70], p=0.20; placental HR 1.59 [95% CI 0.66-3.88], p=0.30). There were no differences in use of adjuvant induction methods, obstetric composite morbidity, blood loss, or length of hospital stay. Retained placenta occurred in 27% (mife+miso) vs 29% (miso) of participants, p=0.36.


Conclusion:
In settings where mifepristone pretreatment is not feasible, simultaneous mifepristone and misoprostol administration did not reduce time to delivery or morbidity compared to misoprostol alone in non-viable second trimester inductions.