Donald Trump thinks women should be able to obtain birth control without a prescription.

“When you have to get a prescription, that's a pretty tough something to climb,” Trump told Dr. Oz in a Thursday interview. “I would say it should not be a prescription. It should not be done by prescription. You have women that just aren't in a position to go get a prescription.”

This is the kind of thing that sounds like a good idea — women often complain that going to the doctor for a birth control prescription seems like an unnecessary burden. The American College of Obstetricians and Gynecologists very clearly endorses moving birth control over the counter.

Still, you shouldn’t expect ACOG or other women’s health groups to start cheering. ACOG, Planned Parenthood, and other advocacy groups have opposed previous Republican efforts to move birth control over the counter.

They argue that proposals like Trump’s could make the Pill more expensive, because insurance plans typically don’t cover non-prescription drugs like Tylenol or Motrin. That means if birth control moved over the counter, women might have to start paying more out of pocket for their contraceptives.

ACOG president Mark DeFrancesco has said proposals like the one Trump outlined “make more women have to pay for their birth control, and for some women, the cost would be prohibitive.”

Why some Republicans support over-the-counter birth control

Over-the-counter birth control emerged as a Republican issue, somewhat surprisingly, in the 2014 midterm race. The Washington Post’s Sandhya Somashekhar wrote at the time:

At least three GOP hopefuls have spoken during the summer in favor of allowing certain types of contraception to be sold without a prescription. Rep. Cory Gardner (R-Colo.), who is challenging incumbent Sen. Mark Udall (D), on Tuesday released a television ad in which he tells a room full of nodding women, “I believe the pill ought to be available over the counter, around the clock, without a prescription. Cheaper and easier for you.”

She spoke with Republican strategist Kellyanne Conway, now Trump’s campaign manager, who said that the endorsement of over-the-counter birth control “probably defangs this increasingly concerted effort by the political left to caricature male Republican politicians as anti-woman, anti-birth control, anti-rainbows and sunshine.”

Gardner introduced a bill in 2015 that would have moved contraceptives over the counter. But the bill stalled in committee — and women’s health groups quickly opposed the issue.

Women’s health groups have opposed Republican efforts to end birth control prescriptions

Women’s health groups generally support ideas to make birth control more accessible, and ACOG endorses over-the-counter birth control. So why would they fight an idea like this once it seems to be getting bipartisan consensus?

ACOG and other women’s health groups, like Planned Parenthood, take issue with how Republicans propose to move birth control over the counter. They worry that making that single policy change would make birth control more expensive, as insurance plans generally don’t cover medications that aren’t prescribed by a doctor.

Just like health insurance plans don’t cover the Tylenol you buy in the pharmacy, they might stop covering birth control pills too. So it’s quite possible that moving birth control over the counter, without a requirement that insurance plans still cover the medication, would actually drive prices up. Here’s how a Princeton economist described the issue to PolitiFact:

Zack Cooper, a health policy and economics professor at Princeton University, said it’s possible that if the pill was reclassified as over-the-counter, consumers would have more options, sales volume would go up and competition would increase between drug companies. These factors can all lead to prices going down. But he said it’s also possible that it has a negative effect, since suddenly consumers are paying for birth control at the point-of-purchase instead of getting it at no cost. "When you make something even a little more expensive, use goes down," Cooper said. "That means more women get pregnant, and babies cost a lot more than birth control. You can argue it would actually increase the cost of insurance and the government will be on the hook for more federal subsidies."

It is possible to have over-the-counter birth control and have insurance coverage. A new California law, for example, allows pharmacists to dispense birth control pills without a prescription — and requires insurance companies to foot the bill.

We haven’t yet heard Trump comment on whether he would endorse mandating that insurers cover birth control if the Pill no longer required a prescription. Until he does, you can expect women’s health groups to give his statement a wary reaction.

Do you think birth control should require a prescription? Tell us why. — Vox (@voxdotcom) September 15, 2016

Watch: why over-the-counter birth control is so necessary