The efficacy of medical abortion: A meta-analysis

Multiple clinical studies demonstrate the efficacy of medical abortion with mifepristone or methotrexate followed by a prostaglandin analogue. However, assessing predictors of success, including regimen, is difficult because of regimen variability and a lack of direct comparisons. This meta-analysis estimates rates of primary clinical outcomes of medical abortion (successful abortion, incomplete abortion, and viable pregnancy) and compares them by regimen and gestational age. We identified 54 studies published from 1991 to 1998 using mifepristone with misoprostol (18), mifepristone with other prostaglandin analogues (23), and methotrexate with misoprostol (13). Data abstracted from studies included regimen details and clinical outcomes by gestational age. We found that efficacy decreases with increasing gestational age (p <0.001), and differences by regimen are not statistically significant except at gestational age greater than or equal to 57 days. For gestations less than or equal to 49 days, mean rates of complete abortion were 94-96%, incomplete abortion 2-4%, and ongoing (viable) pregnancy 1-3%. For gestations of 50-56 days, the mean rate of complete abortion was 91% (same for all regimens), incomplete abortion 5-8%, and ongoing pregnancy 3-5%. For greater than or equal to 57 days, success was lower for mifepristone/misoprostol (85%, 95% confidence interval 78-91%) than for mifepristone/other prostaglandin analogues 95% (CI 91-98%, p = 0.006). For mifepristone/misoprostol, using greater than or equal to 2 prostaglandin analogue doses seems to be better than a single dose for certain outcomes acid gestational ages. We conclude that both mifepristone and methotrexate, when administered with misoprostol, have high levels of success at less than or equal to 49 days gestation but may have lower efficacy at longer gestation. CONTRACEPTION 2000;61:29-40 (C) 2000 Elsevier Science Inc. All rights reserved.