As many as 630,000 Planned Parenthood patients could lose access to birth control, STD screening, and other reproductive health services if the organization loses its federal funding, the Congressional Budget Office estimated Tuesday.

The House is scheduled to vote later this week on the Defund Planned Parenthood Act of 2015, which would bar the federal government from funding the group for one year. In debating the act, there's been significant argument over what would happen to Planned Parenthood patients if the group lost federal funding — whether they would simply transition to other health-care providers or whether they would not find replacements.

CBO, for its part, says it would be a mixed bag: Of Planned Parenthood's 2.6 million patients, the agency estimates that between 130,000 and 630,000 "would face reduced access to care."

"The people most likely to experience reduced access to care would probably reside in areas without access to other health care clinics or medical practitioners who serve low-income populations," the agency concludes.

Planned Parenthood is undeniably a huge provider of birth control, preventive screenings, and other services for low-income women. Researchers at the Guttmacher Institute estimate that in 103 of America's 491 counties, Planned Parenthood is the only safety-net family planning clinic.

It's places like that where CBO expects Planned Parenthood's loss of federal funds would be most severe — and would leave patients for little option to seek similar care elsewhere.