One day before President-elect Donald Trump’s inauguration, the vast majority of House Democrats are warning him to think twice before supporting and signing Republican laws that they say would undermine women’s health care.

letter set to be delivered to Trump on Thursday urges the soon-to-be president to oppose GOP plans in Congress to repeal the Affordable Care Act — which includes measures to prohibit discriminatory insurer practices and expand access to breast-cancer screenings and birth control — and to strip Planned Parenthood of federal funding. It is signed by 174 of 194 House Democrats.

“We urge you to give more thought to how defunding Planned Parenthood and repealing the ACA would harm women in every district in every state,” the letter reads. “Taking these steps would leave all women worse off. As President, you will have the power to prevent this looming disaster. You, more than anyone else, will have to answer to those whose benefits, coverage, and access to care is abruptly ripped away.

“The women of America are watching, Mr. President-elect,” the letter continues. “As are the men who care about them. The true test of whether your policy agenda will harm or help women begins tomorrow.”

The lead signers of the letter are four outspoken Democratic leaders on women’s issues: Reps. Diana DeGette (Colo.), Louise M. Slaughter (N.Y.), Jan Schakowsky (Ill.) and Katherine M. Clark (Mass.).

“The message we’re sending is that we take women’s reproductive rights very seriously, and the next administration needs to do the same,” DeGette said Wednesday. “Women expect to have the health care that they need over the next four years. They expect to have access to a full range of reproductive health care. They expect to have access to family planning, to cancer screening, to all of the critical services that Planned Parenthood provides and that women are able to access under the Affordable Care Act in their insurance plan.”

Congressional Republicans have already started the process of rolling back the ACA, and while Trump pledged in a recent Washington Post interview to provide “insurance for everybody,” plans being discussed on Capitol Hill would remove many of the mandatory coverage provisions that have expanded access to women’s care.

House Speaker Paul D. Ryan (R-Wis.) said this month that Republicans intend to include in the ACA repeal measure a provision that would leave Planned Parenthood, the nation’s largest abortion provider, ineligible to collect federal family planning grants and Medicaid reimbursements for routine medical care. The organization is already banned from spending taxpayer funds on abortions under an appropriations restriction that has been in place since 1976; the new provision could eliminate 40 percent of its annual revenue.

Republicans have signaled they want that money redirected to community health centers that are similarly eligible for Medicaid, but health policy experts have warned that those centers could not immediately absorb the new demand.

“Community health centers cannot pick up the slack here,” Slaughter said Wednesday. “That means hundreds of thousands of people all over the country will be underserved or not served at all.” Hundreds of her constituents, she added, came to a town hall meeting Tuesday co-hosted by Planned Parenthood in Rochester, N.Y., to oppose any changes.

The letter to Trump says many “are fearful about how your presidency will affect women and girls,” citing his pledge to nominate Supreme Court justices who would overturn Roe v. Wade and his Cabinet nominees with “unabashedly anti-woman records.” Trump has said he would support efforts to defund Planned Parenthood but has also spoken positively about the organization as recent as March, when he said at a news conference that it has “done very good work for many, many — for millions of women.”

DeGette said she takes Trump at his word when he says he plans to sign a defunding bill.

“I honestly don’t know what he believes about women’s health; I honestly don’t know what he thinks about Planned Parenthood,” she said. “I do know that the Republicans in Congress have already said they’re going to try to defund Planned Parenthood immediately. . . . You have a Republican majority in the Congress that is hellbent on taking away these services, and you have a president who said he would agree with that. That’s very dangerous.”

This post was updated at 4:30 p.m. to note an additional signer.