Legal experts foresee years of court battles over access to the pills.
Here’s a closer look at the issue.
What is mifepristone?
The U.S. Food and Drug Administration approved mifepristone in 2000 to end pregnancy, when used in combination with a second drug, misoprostol. The combination is approved for use up to the 10th week of pregnancy.
Mifepristone is taken first to dilate the cervix and block a hormone needed to sustain a pregnancy. Misoprostol is taken a day or two later, causing contractions to empty the uterus.
More than half of U.S. abortions are now done with pills rather than with a procedure, according to the Guttmacher Institute, a research group that supports abortion rights. In rare cases, the drug combination can cause excess bleeding, requiring emergency care.