A federal judge in Texas ordered Friday a pause on U.S. approval of the abortion medication mifepristone, raising new questions about getting access to the most common method of abortion in a ruling that waved aside decades of scientific approval.

The immediate impact of the ruling by U.S. District Judge Matthew J. Kacsmaryk, which does not go into immediate effect, is unclear.

What is mifepristone?

Mifepristone is used with another medication called misoprostol to end a pregnancy that is less than 70 days developed. The pills are taken about two days apart.  

Mifepristone stops the “supply of hormones that maintains the interior of the uterus. Without these hormones, the uterus cannot support the pregnancy and the contents of the uterus are expelled,” according to the Mayo Clinic.  

The abortion drug has been used in the United States since 2000 and there is essentially no precedent for a lone judge overruling the medical decisions of the Food and Drug Administration. Mifepristone is one of two drugs used for medication abortion in the United States, along with misoprostol, which is also used to treat other medical conditions.

What happens next to medication abortions?

Kacsmaryk, a Trump administration appointee based in Amarillo, Texas, signed an injunction directing the FDA to stay mifepristone’s approval while a lawsuit challenging the safety and approval of the drug continues.

The judge’s 67-page order gave the government seven days to appeal.

Federal lawyers representing the FDA are expected to swiftly appeal.

Clinics and doctors that prescribe the two-drug combination have said that if mifepristone were pulled from the market, they would switch to using only the second drug, misoprostol.