New laws in Arkansas and Arizona require doctors to inform women that drug-induced abortions can be “reversed” in mid-procedure, a claim that drew charges of “junk science” from abortion-rights groups and many doctors.

The Arkansas law took effect late Monday after Gov. Asa Hutchinson, a Republican, signed it. Arizona Gov. Doug Ducey, also a Republican, signed his state’s bill into law earlier this month.

Supporters say the measures require providers to give women information that could prove critical if they have a change of heart.

“No medical reason exists to deny mothers the opportunity to choose life by sharing with them all their options,” Charmaine Yoest, president of Americans United for Life, said in a written statement. The group developed the model legislation that formed the basis for laws in both states.

The American College of Obstetricians and Gynecologists was among those arguing against the measures.

“Claims of medication abortion reversal are not supported by the body of scientific evidence, and this approach is not recommended in (our) clinical guidance on medication abortion,” says the group’s fact sheet on the Arizona law.

The laws are part of a wave of state legislation aimed at reducing access to abortion rather than banning it outright.

The pharmaceutical abortions targeted in Arkansas and Arizona occur typically occur in the first trimester of a pregnancy. In the U.S., such abortions typically occur in two steps.

First, the woman is given mifepristone, once known as RU-486, which can terminate very early pregnancies and dilate the cervix. A few days later, the second drug, misoprostol, induces contractions to expel the embryo.

In an op-ed in the conservative magazine National Review, Mailee Smith, staff counsel for Americans United for Life, argues that a heavy dose of the hormone progesterone can block the effects of the first drug, permitting the pregnancy to continue normally.

“At this point, it has been reported that 80 babies have been born following the abortion-reversal process, with another 60 or so on the way (still in utero),” Smith wrote.

The obstetrician group, however, said scant evidence supports the claim that progesterone can halt an abortion. A woman who changes her mind mid-abortion, the group said, is better off simply not taking the second drug.

“In 30 percent to 50 percent of women who take mifepristone alone,” the fact sheet says, “the pregnancy will continue.”