Idaho lawmakers want the state to tell people seeking abortions that they can reverse the procedure, a controversial and medically unproven claim that nevertheless has proved popular among opponents of abortion.

On Monday, the Idaho legislature passed a bill mandating that the state’s Department of Health & Welfare supply abortion providers’ patients with information about “interventions, if any, that may affect the effectiveness or reversal of a chemical abortion.” Every single Democrat in both the state Senate and House voted against the measure.

“Women can make up their own minds and they don’t need to have a bunch of information that is misleading and is misguided,” state Rep. Melissa Wintrow told the Spokesman-Review.

In a “chemical” or medication abortion, a patient typically takes two pills, several hours apart. Advocates for “abortion reversal” say that if the patient changes their mind in the middle of the regime, they should skip the second pill and instead take doses of progesterone, a hormone produced by the body during pregnancy.

The mainstream medical community, however, says there’s no evidence this medical procedure works. A paper written by seven doctors from top research hospitals says a study of six women by George Delgado, the San Diego family practice doctor who’s pioneered the idea of abortion reversal, was “of poor quality” and failed to prove that the progesterone would produce anything more than a placebo effect.

“It’s not a totally crazy idea, but that’s not the way medicine works,” Daniel Grossman, an OB/GYN and the director of Advancing New Standards in Reproductive Health at the University of California, San Francisco, told VICE News of the procedure in August. “We don’t just come up with a good idea and start administering that therapy to a patient.”

Instead, if a patient undergoing medication didn’t want to continue the procedure, Grossman said he’d advise them to simply not take the second pill in the abortion regime.

But this hasn’t stopped anti-abortion activists from championing “abortion reversal” anyway. Arizona, Arkansas, and South Dakota all have laws that require providers tell patients that it may be possible to reverse their medication abortions. Americans United for Life, which is known as the “legal arm of the pro-life movement,” created a playbook of model legislation about abortion reversal. And last year, a Trump administration official discussed trying to reverse the abortion of an undocumented teen.

“These are babies we’re talking about. It’s difficult — it’s almost impossible for me to speak because I feel this so strongly,” Rep. Karey Hanks told the Idaho House, according to the Spokesman-Review. “These are pre-born babies. I just want to remind us who are Republicans that in our platform, it talks about right to life, that we reaffirm our support for the sanctity of life from conception to natural death.”