Embryo Survival After Mifepristone: A Systematic Review of the Literature

Rationale: Mifepristone was approved in 2000 by the FDA as an alternative to surgical abortion. In the predominant two drug abortion regimen, mifepristone is followed by misoprostol after one to two days. Little has been published on the survival of living embryos after exposure to mifepristone alone. This review of the literature is undertaken to summarize available studies that define embryo survival after mifepristone. This review defines baseline continuing pregnancy rates after mifepristone, to aid in determining the therapeutic value of supplemental progesterone for women desiring to continue their pregnancy.

Methods: PubMed and the Cochrane Database were searched through March, 2016 for articles that depicted embryo survival after ingestion of mifepristone as a single agent. Further studies were found in the reference lists of relevant articles and review articles. The relevant studies that verified embryo survival utilized ultrasound as a criterion for continuing pregnancy. Results: Of 1855 studies found, 30 studies using mifepristone as a single agent were selected for review. 18 met criteria describing embryo survival. Mifepristone was lethal over a wide range of doses and gestational ages; surviving embryos were present over a similar range. Survival rates using total doses of 200-300 mg ranged from 10-23.3%. In the one study using the current prevailing 200 mg single dose regimen, embryo survival was 23.3%. Regimens with total doses ≥400 mg had embryo survivals ranging from 0-18.1% when followed ≥14 days post mifepristone, and 0-50% when followed for 6-8 days after mifepristone. Embryo survival in studies including gestations up to 70 days was ≤25% in three of four studies.

Conclusion: This literature review shows that mifepristone is an effective embryocidal agent at doses ranging from 200 mg to 600 mg.