A woman in Utah is allowed to have an abortion at 20 weeks. But does she have to give her fetus painkillers in the process?

Yes, the state said Monday, when it became the only state in the nation to require doctors to give anesthesia to women undergoing abortions at 20 weeks or later.

Advocates of the law say that the regulation prevents fetuses from suffering during abortions. But doctors in Utah and elsewhere say there’s no proof that fetuses are able to feel anything at that point in pregnancy, and that sedating women during the procedure puts them at risk of complications.

“You’re now mandating [women] take that risk, based on inconclusive and biased evidence. You don’t understand what you’re legislating,” Dr. Sean Esplin, a doctor with Intermountain Healthcare in Utah, testified at committee hearing on the bill earlier this month.

The bill’s sponsor, state Sen. Curt Bramble (R-Provo), said he initially hoped to ban abortions after 20 weeks, but he was told that such a law would probably challenged on constitutional grounds. This measure was next best option, he told the Salt Lake Tribune; it requires doctors to take steps to “eliminate or alleviate organic pain to the unborn child” except for in cases when the abortion is necessary to prevent the health of the mother, when the fetus suffers from a deadly congenital defect, or when the administration of anesthetic might put the mother at risk.

“In this quote ‘medical procedure,’ let’s call it what it is. It’s killing babies. And if we’re going to kill that baby, we ought to protect it from pain,” Bramble said.

This is a new twist on an old argument: For years, antiabortion advocates have used the fetal pain argument to justify bans on abortion 20 weeks after conception. According to the National Right to Life Committee, “pain-capable unborn protection” laws are currently on the books in 12 states (though they’re being challenged in two).

But the idea that 20-week-old fetuses can feel anything is disputed; a 2005 review of more than 300 studies published in the Journal of the American Medical Association concluded that fetal perception of pain is unlikely before the third trimester (28 weeks).

Utah generally does not allow abortions after the point of viability, around 22 to 24 weeks.

Esplin told the Associated Press that the new law means that any anesthetic or analgesic will have to be administered to the mother; women having abortions will either be placed under general anesthesia — meaning they’re unconscious and hooked up to a breathing tube — or sedated with a heavy dose of narcotics. Previously, women were given a choice to be anesthetized.

General anesthesia carries its own side effects and risks, and doctors say they try to avoid it except in cases where it’s absolutely necessary.

“You never give those medicines if you don’t have to,” David Turok of the University of Utah’s obstetrics and gynecology department told the AP.

Turok and some lawmakers have expressed concern that the rule could be interpreted as mandating that pregnant women be anesthetized for all procedures that happen after 20 weeks of pregnancy. Utah law defines abortions as “the intentional termination or attempted termination of human pregnancy” through a medical procedure carried out by or ordered by a physician — loosely interpreted, that could include instances of induced labor, such as when a woman is past her due date.

State Sen. Brian Shiozawa (R-Cottonwood Heights), who is also an emergency room doctor, told the Deseret News earlier this month that if the law was passed, “you can forget natural birth and labor” because there’s probably pain to a fetus coming down the birth canal as well.

In an interview with the Salt Lake Tribune, Shiozawa said he is “all for” changing the statutes on abortion. But this bill, he added, was “cumbersome” for women and their doctors.

The new law makes Utah the only state in the country where women must undergo anesthesia to have an abortion. The Montana legislature passed a similar law last year, but it was vetoed by the state’s democratic governor Steve Bullock.

Utah’s governor, Gary Herbert (R), who signed the bill into law Monday, said last month that rather than get into a debate about abortion, he just wanted to address the question: “If we’re going to have abortion, what is the most humane way to do it?”

“Fetuses have a heartbeat after about five weeks. And the idea of just being callous about that should cause all of humanity concern” regardless of their stance on abortion, he continued.

Though the new law is controversial, its impact will likely be limited, Karrie Galloway, executive director of Planned Parenthood of Utah, told the Salt Lake Tribune. In 2014, the last year for which data is available, only 17 Utah women had abortions after 20 weeks. Planned Parenthood is the only provider in the state that provides abortions during the window covered by the law.

But Galloway said the idea that lawmakers with no medical knowledge are dictating what women and their doctors can do “is what’s infuriating.”

“I mean, we have fetal medical specialists speaking and they were discounted by a citizen who said, ‘I read it on the Internet and therefore it must be true,'” she said. “That’s how we do policy here in Utah.”