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:

  1. Uterine lining thinning
  2. Pregnancy detachment
  3. Cervical softening and dilation
  4. 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

If you have questions about medication abortion, please visit our page on frequently asked questions.

Please contact us with suggestions, updates, or link requests at medicationabortion@ibisreproductivehealth.org

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Last updated: September 2009