(CNN) Utah will now require doctors to provide anesthesia to women having abortions at 20 weeks of pregnancy or later.

The law, which experts say is the first of its kind in the nation, is based on the scientifically disputed notion that a fetus can feel pain during the procedure.

"The governor is adamantly pro-life," said a statement from Gov. Gary Herbert's office. "He believes in not only erring on the side of life, but also minimizing any pain that may be caused to an unborn child."

Gov. Gary Herbert signed a bill making Utah the first state to require doctors to give anesthesia to women having an abortion at 20 weeks of pregnancy or later.

Experts in the medical community and abortion rights activists blasted the measure, saying it will interfere with the relationship between a physician and a patient and promotes the medically unproven theory about fetal pain.

Dr. Anne Davis, the consulting medical director for Physicians for Reproductive Health , said she believes no ethical doctor is going to give powerful drugs to a patient if it could harm the patient's health.

"Imagine that I sit down with a patient and tell her what she can expect and how I'm going to take care of her and somehow I work in, 'Oh, by the way, the state has told me that I have to give this to you?' She asks, 'Why?' And I say, 'There's no benefit to you, but there will be additional risk.'"

"How as a doctor do I live with that? This law is about stopping abortion," Davis said. "This is just another measure to deter women from getting abortions."

'Fetal pain' laws

Utah's law marks the first time legislation mandating anesthesia has passed, said Elizabeth Nash, a policy expert with the research organization the Guttmacher Institute. It would be a third-degree felony not to administer anesthesia to women seeking abortions who are 20 weeks along, according to the new law.

But Utah's measure is not the first time states have used the theory of fetal pain as justification to ban abortion at 20 weeks.

Fifteen states have moved to do that but only 12 actively ban the procedure after that time because three states are facing court challenges to laws.

The 12 states that ban abortions after 20 weeks are Alabama, Arkansas, Indiana, Kansas, Louisiana, Mississippi, Nebraska, North Dakota, Oklahoma, Texas, West Virginia, and Wisconsin. The three states facing court challenges are Arizona, Georgia and Idaho.

In Utah, Republican Sen. Curt Bramble , who is against abortion, sponsored the legislation. Gov. Herbert signed it Monday.

When asked if there is a cost estimate for the new anesthesia requirement or if the state government will provide subsidies to cover that expense, the governor's spokeswoman, Aimee Edwards, referred CNN to the Utah Department of Health

The spokesman for that department, Tom Hudachko, said there was not a fiscal note attached to the bill, and the department does not have funding to pay for anesthesia.

Nash, of the Guttmacher Institute, said Utah's law could mean a "de facto" ban on abortions at 20 weeks or later because no doctor is going to give a patient anesthesia who doesn't need it.

Scientific research doesn't support fetal pain theory

"Sound health policy is best based on scientific fact and evidence-based medicine. The best health care is provided free of governmental interference in the patient-physician relationship. Personal decision-making by women and their doctors should not be replaced by political ideology," said Dr. Hal C. Lawrence, the organization's executive vice president and CEO.

The group cited a rigorous 2005 scientific review published in the Journal of the American Medical Association that said fetal perception of pain is unlikely before the third trimester and no studies since 2005 demonstrate fetal recognition of pain.

"Little or no evidence addresses the effectiveness of direct fetal anesthetic or analgesic techniques," according to the research in JAMA. "Similarly, limited or no data exist on the safety of such techniques for pregnant women in the context of abortion. Anesthetic techniques currently used during fetal surgery are not directly applicable to abortion procedures."

Bramble said "science isn't settled" on the issue, and he believes that if there's even a chance that a fetus may feel pain then his bill is beneficial.

If a woman doesn't want to have anesthesia before an abortion for whatever reason, "then that individual patient might not want to decide to have that abortion in Utah," he said.

Dr. Sara Imershein, an obstetrician and gynecologist in Washington, D.C., said she and her colleagues routinely provide pain management options for their patients, and those options are chosen based on a patient's individual health needs.

"It concerns me that we have personal political and ideological agendas on an absurd law. This law is designed to mislead patients against what is scientifically shown to be true," she said. "Women's health is medical, not political."