Prior Cesarean Birth and Risk of Uterine Rupture in Second-Trimester Medication Abortions Using Mifepristone and Misoprostol

Abstract

OBJECTIVE: To assess the risk difference of uterine rupture when using current mifepristone and misoprostol regimens for second-trimester abortion among individuals with prior cesarean birth compared with those without prior cesarean birth. DATA SOURCES: We searched the terms second trimester, induction, mifepristone, and abortion in PubMed, EMBASE, POPLINE, ClinicalTrials.gov, and Cochrane Library from inception until December 2022. METHODS OF STUDY SELECTION: We included randomized trials and observational studies including a mixed cohort, with and without uterine scar, of individuals at 14–28 weeks of gestation who used mifepristone and misoprostol to end a pregnancy or to manage a fetal death. We excluded case reports, narrative reviews, and studies not published in English. Two reviewers independently screened studies. TABULATION, INTEGRATION, AND RESULTS: Absolute risks with binomial CIs were calculated from pooled data. Using R software, we estimated total risk difference by the Mantel–Haenszel random-effects method without continuity correction. For studies with zero events, a continuity correction of 0.5 was applied for individual risk differences and plotted graphically with forest plots. Statistical heterogeneity was assessed with Higgins I 2 statistics. Funnel plot assessed for publication bias. Of 198 articles identified, 22 met the inclusion criteria: seven randomized trials (n=923) and 15 observational studies (n=6,195). Uterine rupture risk with prior cesarean birth was 1.1% (10/874) (95% CI 0.6–2.1) and without prior cesarean birth was 0.01% (2/6,244) (95% CI 0.0–0.12). The risk difference was 1.23% (95% CI 0.46–2.00, I 2=0%). Of the 12 reported uterine ruptures, three resulted in hysterectomy. CONCLUSION: Uterine rupture with mifepristone and misoprostol use during second-trimester induction abortion is rare, with the risk increased to 1% in individuals with prior cesarean birth. SYSTEMATIC REVIEW REGISTRATION: PROSPERO, CRD42022302626.