The Republican proposal to replace the Affordable Care Act would bar people from using federal tax credits to buy health insurance plans that cover abortion.

If the measure is passed, abortion rights advocates fear it could compel insurers to stop offering abortion coverage at all.

“There’s no reason insurers would sell any plans that cover abortion because everyone would be wanting to use these tax credits,” said Adam Sonfield, a senior policy manager for the Guttmacher Institute, a research center that works to promote access to abortion.

For now, the proposal would create a big problem for two of the largest and most liberal states: California, where state law requires insurers to cover abortion, and New York, which has long encouraged coverage by including it in its model plan of what insurers have to cover. Massachusetts, too, has long indicated that insurers should cover abortion as “medically necessary.”