How does medication abortion work?

Regimen or procedure	Mechanism of action	Advantages	Disadvantages
Mifepristone and misoprostol	Mifepristone is taken orally and blocks the action of progesterone. This results in: Uterine lining thinning Pregnancy detachment Cervical softening and dilation Uterine contractions Subsequent administration of oral, vaginal, or buccal misoprostol, a prostaglandin E₁analogue, results in uterine contractions and expulsion of the products of conception.	High success rate (95%-98%) Effective during early pregnancy (through nine weeks) For many women, the process resembles a heavy period For many women, considered more "private" Usually avoids surgical intervention Anesthesia not required	May take days and occasionally weeks for the abortion to complete Efficacy decreases at later gestational ages Light bleeding may continue for several weeks after the abortion is complete Women may see blood clots and the products of conception Sometimes requires at least two clinic visits Mifepristone can be expensive Mifepristone is not available in most countries
Methotrexate and misoprostol	Methotrexate is anti-metabolite that inhibits DNA synthesis. Given by injection or taken orally, methotrexate interferes with the implantation process. Subsequent administration of oral or vaginal misoprostol, a prostaglandin E₁ analogue, results in uterine contractions and expulsion of the products of conception.	High success rate (95%) if used in the first seven weeks of pregnancy Often considered to be more "private" Usually avoids aspiration intervention Anesthesia not required Treats ectopic pregnancy	Requires at least two clinic visits Often takes weeks to complete (longer than the mifepristone and misoprostol regimen) Post-procedure bleeding may last for weeks Efficacy decreases significantly after 7 weeks gestation (from 95% to 82% efficacy) Women may see blood clots and the products of conception Methotrexate is not available in all countries
Misoprostol alone	Misoprostol is a prostaglandin E ₁ analogue that causes uterine contractions and cervical softening. Administration of vaginal or buccal misoprostol alone results in uterine contractions and expulsion of the products of conception.	Used during early pregnancy (through nine weeks) For many women, the process resembles a heavy period Often considered to be more "private" Usually avoids aspiration intervention Anesthesia not required Registered in many more countries than either mifepristone or methotrexate Often much cheaper than other medication abortion methods	Success rate is low (75%-85%) compared to other medication abortion regimens Research to determine optimal regimen is still underway Takes days to weeks to complete Cramping and bleeding more significant than other medication abortion regimens Post-procedure bleeding my last for weeks Women may see blood clots and the products of conception
Vacuum aspiration procedures	A straw-like tube (a cannula), which is attached to a suction apparatus is inserted into the uterus through the open (dilated) cervix. The uterine contents are then emptied by suction.	Very high success rate (99%) Often requires only one clinic visit Procedure completed within minutes Sedation is available	Involves instrumentation and a procedure Often considered to be less "private" May not be widely available, particularly in developing countries