What is the continuing pregnancy rate after mifepristone alone?

The American College of Obstetricians and Gynecologists (ACOG) states that “as many as half of women who take only mifepristone continue their pregnancies”.1 However, the evidence below shows that the continuing pregnancy rate after ingesting mifepristone alone is generally below ≤25 percent for gestational ages ≤49 days.

Since 2015, there have been five Abortion Pill Rescue (APR) scoping and systematic reviews (Creinin 20192; Davenport 20173; DeBeasi 20234; Grossman 20155; Stifani 20236). These reviews report the continuing pregnancy rate after mifepristone alone using data from mifepristone efficacy studies published in the 1980s and 1990s (refer to APRScience.org/Studies to view a collection of references for these studies). In total, the five reviews cited 16 mifepristone efficacy studies.

Twelve of the sixteen mifepristone efficacy studies confirmed the presence of a living embryo using ultrasound. These twelve studies are shown in the chart. The other four studies (Birgerson, Grimes, Swahn, Zheng) either did not measure continuing pregnancy or used an imprecise method that may have overstated the actual continuing pregnancy rate. These four studies were not included in the chart. View dataset 1 for results from all sixteen studies.

Some mifepristone efficacy studies published data for more than one dose, resulting in 17 dosage groups across the 12 studies. The chart on this page shows the continuing pregnancy rate for each of the twelve efficacy studies comprising 17 dosage groups that confirmed the presence of a living embryo using ultrasound. The continuing pregnancy rate never exceeded 25 percent, except for Elia, regardless of the mifepristone dose, gestational age, or follow-up period. Studies with a shorter follow-up period after the last mifepristone dose, such as Elia (2 days after the last mifepristone dose), tended to have higher embryo survival rates and vice-versa. Note that continuing pregnancy rates are considerably lower for a combined mifepristone plus misoprostol regime. The FDA reports that ongoing pregnancy is 0.7% – 0.9% through 70 days gestation for a combined mifepristone plus misoprostol regime.7

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  1. Medication Abortion Reversal Is Not Supported by Science. https://www.acog.org/advocacy/facts-are-important/medication-abortion-reversal-is-not-supported-by-science. ↩︎
  2. Creinin, Mitchell D., and Melissa J. Chen. 2019. “Mifepristone Antagonization Requires Real Studies to Evaluate Safety and Efficacy.” Contraception 100, no. 6: 427–29. https://doi.org/10.1016/j.contraception.2019.10.016. ↩︎
  3. Davenport Mary, Delgado George, Harrison Matthew P., Khauv Veronica. 2017. Embryo Survival After Mifepristone: A Systematic Review of the Literature. Issues in Law & Medicine 32 (1): 3‐18. PMID: 29108160. https://pubmed.ncbi.nlm.nih.gov/29108160/ ↩︎
  4. DeBeasi, Paul L. C. 2023. Mifepristone Antagonization with Progesterone to Avert Medication Abortion: A Scoping Review. The Linacre Quarterly, May, 002436392311765. https://journals.sagepub.com/doi/10.1177/00243639231176592. ↩︎
  5. Grossman Daniel, White Kari, Harris Lisa, Reeves Matthew, Blumenthal Paul D., Winikoff Beverly, Grimes David A. 2015. Continuing Pregnancy After Mifepristone and ‘Reversal’ of First-Trimester Medical Abortion: A Systematic Review. Contraception 92 (3): 206‐211. https://pubmed.ncbi.nlm.nih.gov/26057457/ ↩︎
  6. Stifani, Bianca Maria, and Antonella Francheska Lavelanet. 2023. Reversal of Medication Abortion with Progesterone: A Systematic Review. BMJ Sexual & Reproductive Health, October, bmjsrh-2023-201875. https://doi.org/10.1136/bmjsrh-2023-201875. ↩︎
  7. FDA. 2016. “MIFEPREX (mifepristone) Medication Guide.” https://www.accessdata.fda.gov/drugsatfda_docs/label/2016/020687s020lbl.pdf. ↩︎