Medication abortion regimens are safe and effective during
early pregnancy. For all three methods of
medication abortion, efficacy decreases with increasing gestational
age. The mifepristone and misoprostol regimen is 95%-98% effective through the first nine weeks of
pregnancy. Recent research indicates that mifepristone and misoprostol can be used in the tenth week of pregnancy but with somewhat lower efficacy (≈92%).
The methotrexate and misoprostol regimen is highly
effective in the first seven weeks of pregnancy (95%) but is less
effective after 49 days (82% during the eighth week of pregnancy).
The
efficacy of misoprostol alone is variable and depends on both
gestational age and regimen
(65%-93%). The most recent studies on the use of misoprostol alone for early pregnancy termination report efficacy of 75%-85% through the first nine weeks. This efficacy is based on a regimen that is comprised of three 800 microgram doses taken 3 to 12 hours apart and administered bucally, sublingually, or vaginally. Alternatively, similar efficacy can be achieved with vaginal administration of 800 micrograms of misoprostol followed 24 hours later with another 800 micrograms administered vaginally.
