Objective We conducted a systematic review of the literature on the effectiveness of medical abortion "reversal" treatment. Since the usual care for women seeking to continue pregnancies after ingesting mifepristone is expectant management with fetal surveillance, we also performed a systematic review of continuing pregnancy after mifepristone alone. Study design We searched PubMed, CINAHL (Cumulative Index to Nursing and Allied Health Literature), Scopus and the Cochrane Library for articles published through March 2015 reporting the proportion of pregnancies continuing after treatment with either mifepristone alone or after an additional treatment following mifepristone aimed at reversing its effect. Results From 1115 articles retrieved, 1 study met inclusion criteria for abortion reversal, and 13 studies met criteria for continuing pregnancy after mifepristone alone. The one report of abortion reversal was a case series of 7 patients receiving varying doses of progesterone in oil intramuscularly or micronized progesterone orally or vaginally; 1 patient was lost to follow-up. The study was of poor quality and lacked clear information on patient selection. Four of six women continued the pregnancy to term [67%, 95% confidence interval (CI) 30-90%]. Assuming the lost patient aborted resulted in a continuing pregnancy proportion of 57% (95% CI 25-84%). The proportion of pregnancies continuing 1-2 weeks after mifepristone alone varied from 8% (95% CI 3-22%) to 46% (95% CI 37-56%). Continuing pregnancy was more common with lower mifepristone doses and advanced gestational age. Conclusions In the rare case that a woman changes her mind after starting medical abortion, evidence is insufficient to determine whether treatment with progesterone after mifepristone results in a higher proportion of continuing pregnancies compared to expectant management. Implications Legislation requiring physicians to inform patients about abortion reversal transforms an unproven therapy into law and represents legislative interference in the patient-physician relationship.