On Tuesday, Donald J. Trump said he wanted Congress to repeal the Affordable Care Act right away and replace it with a new plan “very shortly thereafter.” But before they abandon all the work that has gone into the health care law since 2010, President-elect Trump and Republicans in Congress owe Americans a detailed explanation of how they plan to replace it. They should not repeal the law until they have submitted their replacement proposal for analysis by nonpartisan authorities like the Congressional Budget Office and the Tax Policy Center to determine how it will affect health insurance coverage, state and federal finances and individual tax burdens.

Vague promises are not enough when we are considering enormous changes in this country’s $3 trillion medical economy. Here are seven important questions that Congress must answer about its replacement plan before repealing the Affordable Care Act:

1. How many millions of Americans will lose coverage? The A.C.A. expanded Medicaid coverage to around 12 million people in 31 states and the District of Columbia, and provided financial assistance for moderate-income Americans to buy insurance. These measures have reduced the percentage of Americans who are uninsured to the lowest levels in history. Proposals by Tom Price, Mr. Trump’s choice to run Health and Human Services, and by the House speaker, Paul D. Ryan, would repeal the expansion of Medicaid and replace the A.C.A.’s income-based subsidies with less generous tax credits. Another plan from the House Republican Study Committee would offer deductions. We particularly need to know how this would affect low-income Americans, to whom tax deductions are nearly worthless, and who would generally not be able to afford coverage under these plans.

2. Will people over 55 pay higher health premiums for the same coverage? Under the health care law, premiums for older people cannot be more than three times as much as premiums for younger people. But the Ryan plan would let insurers charge older people five times as much. This change, combined with smaller tax credits or deductions that would not compensate for the increased cost, would significantly increase health care costs for many older Americans.

3. Will the new plan let insurers charge women higher premiums than men while offering them less coverage? Before the A.C.A. banned gender-based premiums, insurers in many states charged women more than men of the same age — some as much as 50 percent more. The A.C.A. also required all insurers to cover preventive health services without co-payments; for women, this includes birth control, Pap smears, mammograms and a host of other crucial services. Maternity care is fully covered as well. Republican replacement plans offer no such protection. And many Republicans want to defund Planned Parenthood, too, which would deprive women not just of coverage but also of care.