What to know about mifepristone after Supreme Court strikes down legal challenge to abortion pill

The U.S. Supreme Court unanimously rejected on Thursday a bid by a group of antiabortion doctors that would have potentially blocked widespread access to a common abortion pill.

In the opinion, written by Justice Brett Kavanaugh, the court determined that the group had no legal standing to challenge the U.S. Food and Drug Administration's (FDA) regulation of mifepristone.

Here’s what to know about the mifepristone, including how it works and how common it is.

Mifepristone is an oral drug typically used in combination with another drug, misoprostol, to induce an abortion or to help manage an early miscarriage.

The medication works by blocking progesterone, a hormone that the body needs to continue a pregnancy.

This causes the uterine lining to stop thickening and to break down, detaching the embryo. The second drug, misoprostol, taken 24 to 48 hours later, causes the uterus to contract and dilates the cervix, which will expel the embryo.

The FDA authorized mifepristone -- sometimes called by the brand name Mifeprex -- for medication abortion in September 2000 for up to seven weeks' gestation, which was then extended to 10 weeks' gestation in 2016.

However, the World Health Organization says the two drug-regimen can be taken up until the 12-week mark of pregnancy.

In 2019, the FDA approved a generic version of the drug.

Medication abortion now accounts for more than half of all abortions in the U.S., according to the Guttmacher Institute, a research group focusing on sexual and reproductive health.

As of 2023, medication abortions account for 63% of abortions performed in the U.S., up from 24% in 2011, the data from Guttmacher shows.

Mifepristone is safe and effective when used as indicated and directed by the FDA, the agency said. When used in combination, mifepristone and misoprostol are nearly 97% effective at terminating a pregnancy, according to a 2015 systematic review from the University of California, Davis.

In December 2021, the FDA announced it permanently lifted its restriction that abortion pills had to be dispensed in-person. In January 2023, it went further by allowing retail pharmacies to provide the drug too, either by mail or in person, so long as they meet certain requirements.

Mifepristone is not recommended if a woman is more than 70 days out from their last menstrual period or if they have an ectopic pregnancy, have problems with glands near the kidney, have bleeding problems, are taking blood thinning medication, have an IUD in place or have had an allergic reaction to mifepristone.