How medical abortion with RU-486/mifepristone works

A step-by-step guide on how these drugs terminate pregnancy

Photo credit: Mesa Schumacher advert

Editor’s note (3/15/23): A Texas judge will today hear arguments in a case that could limit access to the abortion drug mifepristone and threaten the authority of the US Food and Drug Administration. In this opinion piece published last year, we explained how mifepristone works in combination with the drug misoprostol.

In 2016, the US Food and Drug Administration approved a two-drug combination of Mifeprex (also called RU-486 or mifepristone) and Cytotec (commonly known as misoprostol) to induce non-surgical termination of pregnancy. In 2019, the Centers for Disease Control and Prevention reported that about 42 percent of all abortions in the United States were medical.

To start the process, a person takes mifepristone within 10 weeks of their last period. A day or two later they take misoprostol. Both drugs work individually, but together they are more effective. Mifepristone blocks the effects of progesterone on the uterus, rendering it unable to support pregnancy. Misoprostol triggers, among other things, uterine contractions.

Photo credit: Mesa Schumacher

Research has shown that medical abortions are safe and effective. According to a 2015 study by the University of California, Los Angeles, 99.6 percent of more than 30,000 women who sought a medical abortion were able to terminate their pregnancy. In a 2013 review of clinical trials using mifepristone and misoprostol together, only 0.3 percent of the more than 45,000 women studied had complications that required hospitalization. Treatment occasionally failed when pregnancy lasted more than eight weeks or when directions were not followed. The mortality rate of the drugs is less than 0.001 percent.

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ABOUT THE AUTHORS)

Megha Satyanarayana is the Editor-in-Chief of Scientific American. Follow her on Twitter @meghas

Recent Articles by Megha Satyanarayana

Mesa Schumacher is a medical illustrator and science artist with a passion for clear communication and engaging imagery. She is the main artist of Mesa Studios. Her work can be found in magazines, books, magazines, museums, zoos, aquariums and educational games.

Recent articles by Mesa Schumacher

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