Background: We sought to determine whether there is evidence to recommend progesterone for individuals not wishing to complete a medication abortion after taking mifepristone.
Methods: We undertook an updated systematic review including a primary search for studies in which individuals received progesterone to reverse the effects of mifepristone, and a secondary search for studies in which individuals received mifepristone alone. We searched PubMed, Embase, Cochrane, CINAHL and grey literature up to December 2022. We used the Joanna Briggs Institute critical appraisal tools for risk of bias assessment. We compared ongoing pregnancy rates among individuals treated with progesterone to those managed expectantly.
Results: We did not find new studies in our secondary search. For the main search, we included three case series and one randomised controlled trial. Data were available for 561 individuals who received progesterone after mifepristone, of whom 271 (48%) had ongoing pregnancies. The quality of the evidence in the case series was low due to methodological and ethical issues. Enrollment in the randomised trial stopped early due to bleeding events in both arms. The ongoing pregnancy rate for individuals ≤7 weeks who received progesterone was 42% (95% CI 37-48) compared with 22% (95% CI 11-39) for mifepristone alone. At 7-8 weeks, the ongoing pregnancy rate was 62% (95% CI 52-71) in the progesterone group and 50% (95% CI 15- 85) in the mifepristone alone group.
Conclusion: Based mostly on poor-quality data, it appears the ongoing pregnancy rate in individuals treated with progesterone after mifepristone is not significantly higher compared to that of individuals receiving mifepristone alone.
Keywords: Abortifacient Agents; Mifepristone; abortion, induced.
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