WASHINGTON—The Trump administration proposed a new set of rules on Friday paring protections for transgender patients in health-care settings, part of a legal effort by the administration to more narrowly define the scope of sex discrimination.

The new rules would end an Obama-era policy expanding an antidiscrimination provision in the Affordable Care Act to cover bias against people who identify with a gender other than the one listed on their birth certificate. The Obama-era rule, issued in 2016, was blocked by a federal judge in Texas who said the law didn’t extend civil-rights protections to transgender people.

The Department of Health and Human Services’ Office for Civil Rights said it was changing the policy to more closely hew to the ACA text, which doesn’t explicitly mention gender identity as a protected category in health care.

“When Congress prohibited sex discrimination, it did so according to the plain meaning of the term, and we are making our regulations conform,” said Roger Severino, director of the Office for Civil Rights. The rule will likely be finalized after a 60-day public comment period.

Critics say the change would make it easier for doctors and hospitals, citing religious or other reasons, to discriminate against and reduce access to care for transgender people. It also could allow health-insurance companies to deny coverage of certain procedures, such as hormone therapies or hysterectomies, to people who identify as transgender.