Mifepristone priming and subsequent misoprostol for second trimester medical abortion in women with previous caesarean delivery

Aims: To assess clinical outcomes and complications in women with >= 1 prior caesarean delivery (CS) during mid-pregnancy medical abortion with misoprostol following mifepristone priming. Materials and Methods: Retrospective analysis of abortions at 13-28 weeks gestation using sequential mifepristone and misoprostol at a single centre from 1/2008-12/2018. Procedural outcomes were compared between cases with no prior CS, one prior and >= 2 prior CS. Results: There were 1399 consecutive women who underwent a medical abortion, with 304 (21.7%) having >= 1 prior lower segment CS (241 one, 49 two, 12 three, one four) and one a prior classical CS. Median gestation was 19 weeks (interquartile range (IQR) 17-21) among nulliparas, multiparas with no prior CS and multiparas with prior CS, P = 0.505. Compared with nulliparas (median procedural duration 10.8 h, IQR 7.5-16.5; adjusted hazards ratio (aHR) = 1.20 95%CI 1.04-1.40, P = 0.015), multiparas with prior CS had a shorter procedural duration (9.5 h, IQR 6.5-13.5) while multiparas with no CS had the shortest duration (7.0 h, IQR 5.0-9.8; aHR = 2.28 95%CI 2.01-2.58, P < 0.001). Complications were more frequent with prior CS: estimated blood loss (medians: 100 cc no CS vs 150 cc >= 1 CS, P = 0.002), blood loss >1000 cc (3.6% no CS vs 7.2% >= 1 CS; odds ratio (OR) >= 2.11 95%CI 1.23-3.62, P = 0.007) and placental retention (17.3% no CS vs 25.3% >= 1 CS; adjusted OR = 1.44 95%CI 1.05-1.99, P = 0.024). Uterine rupture occurred in 4/304 women with >= 1 prior CS (1.3%). Conclusions: Mifepristone-misoprostol abortion in women with prior CS is generally safe but associated with an increased risk of procedural complications. Lowering of the misoprostol dosage with prior CS may reduce uterine rupture, although this hypothesis requires ongoing research.