Under federal law, states have to cover abortion costs for Medicaid beneficiaries who’ve gotten pregnant through rape or incest. But for the last 25 years, South Dakota hasn’t done that.

That fact was one of the more striking findings uncovered in a report released this month by federal investigators at the nonpartisan Government Accountability Office. The report, which broadly examined abortion access across the country, also dove into whether states are complying with Medicaid requirements. Thanks to a federal law known as the Hyde Amendment, federal dollars typically cannot be used to pay for abortion services, but state Medicaid programs must cover the cost of an abortion if the pregnancy either endangers the life of the woman or if it’s the result of rape or incest.

If someone is seeking an abortion in one of those circumstances, state Medicaid programs must cover a pill that induces abortions, called Mifeprex. But in another example of flouting federal rules, 13 states and Washington, D.C. won’t pay for the medication, the report discovered.

“Without such coverage, Medicaid beneficiaries seeking abortions in these states would have to find another way to pay for the drug or undergo a surgical abortion instead,” the report noted.

The Centers for Medicare and Medicaid Services, which oversees Medicaid, didn’t know that so many states were out of compliance, according to the report — though it did know about South Dakota. The federal agency first sent a letter to South Dakota about the problem back in 1994, according to the report, but hasn’t done anything to force the state to comply with federal regulations.

Some states also require that people seeking abortions fulfill more requirements, such as having a health care provider certify that the pregnancy is due to rape or incest, before they can get their procedures covered by Medicaid. (Under federal law, physicians must certify that continuing a pregnancy would endanger a patient’s life; if a state wants to require certifications in other circumstances, they’re generally free to do so.) Fourteen states even require that survivors of rape or incest file a report with either police or another public agency before they receive coverage for abortions.

It’s unclear just how many people are getting their abortions covered through Medicaid, since state reports on the matter are often inaccurate or incomplete. In the Centers for Medicare and Medicaid Services’ annual reports to Congress, the agency says that federal funding is claimed in about 550 abortions. The Government Accountability Office report, however, found that states claimed federal funding for almost 5,000 abortions between fiscal year 2013 and fiscal year 2016.

Among the report’s other findings:

Twenty-one states will use their own funds to cover abortions in circumstances beyond rape, incest, or life endangerment.

In interviews with eight providers, federal investigators found that six said they often didn’t even submit claims for state Medicaid reimbursements because it’s so challenging and because states frequently deny claims anyway.

Fifteen states gave investigators information about how many Medicaid claims they denied. About half of those states denied claims 60 percent or more of the time, the report found. Investigators didn’t ask states why they denied claims, but a few provided it anyway — and the denials sometimes stem from stringent federal regulations. For example, one state said that if a claim for abortion in the case of life endangerment lacked the Medicaid beneficiary’s address, the state would automatically deny the claim, as the feds require.