The FDA in 2000 approved mifepristone to terminate pregnancies of up to 10 weeks, when used with a second drug, misoprostol. Mifepristone is taken first to dilate the cervix and block the hormone progesterone, which is needed to sustain a pregnancy. Misoprostol is taken 24 to 48 hours later, causing the uterus to contract and expel pregnancy tissue.

Bleeding is a common side effect, though serious complications are very rare. The FDA says more than 3.7 million U.S. women have used mifepristone since its approval.

the pills are most often recommended for pregnancies less than 10 or 11 weeks.