The “abortion pill” isn’t one pill, but two pills taken in sequence. First, women visit a clinic and take mifepristone, which blocks progesterone. Then, one to two days later, the drug misoprostol can be used to induce an abortion at home. The entire process—known as medical, rather than surgical, abortion—is safe, effective, and increasingly common.

In recent years, the rise of medical abortion has led some anti-abortion activists and lawmakers to claim that the process can be reversed with an emergency treatment after the first pill. But even if they succeed at turning that myth into law, the truth is that science is not on their side.

As WWL reported, the Louisiana House of Representatives unanimously passed a resolution on Monday that asks the state’s Department of Health and Hospitals to study the possibility of reversing a medical abortion.

If the bill passes the state Senate, Louisiana could join Arizona, South Dakota, and Arkansas in legislating on the topic of so-called abortion reversal.

Arizona’s new law, as The Daily Beast’s Brandy Zadrozny reported last March, requires doctors to tell women that they can change their minds during the medical abortion process. The American Civil Liberties Union (ACLU) is now challenging that law in court. South Dakota and Arkansas also require women to be advised that they can reverse their medical abortions.

It is impossible to find reliable sources for the notion that medical abortions can be reversed. The Louisiana bill’s sponsor, Rep. Frank Hoffman, told WWL that he heard about it from George Delgado, the medical director of an organization called Abortion Pill Reversal (APR), at a Right to Life Conference in New Orleans.

APR targets women who have taken mifepristone but not yet ingested misoprostol, urging them to “call now” for emergency treatment. That treatment consists of an ultrasound to check whether or not the pregnancy has been terminated followed by a large dose of progesterone to—in theory—reverse the effects of mifepristone. The progesterone can be injected into the butt muscle, taken orally, or inserted into the vagina.

APR claims this treatment is successful in a slight majority of cases, with pregnancies ending anyway 45 percent of the time. But even if APR’s reported success rate is true, that’s still not proof that the emergency progesterone injection is doing the trick.

As the American College of Obstetricians and Gynecologists (ACOG) notes, mifepristone alone is often insufficient to induce an abortion (PDF). There is a reason, after all, that there are two pills involved in a standard medical abortion. In up to 50 percent of cases, ACOG reports, a woman’s pregnancy will continue even after taking the first pill.

That means that groups like APR can claim to be “reversing” abortions in cases where pregnancies are simply continuing as they normally would. Simply put, it would be akin to taking credit for a coin flip.

Or, as ACOG observed, “Available research seems to indicate that in the rare situation where a woman takes mifepristone and then changes her mind, doing nothing and waiting to see what happens is just as effective as intervening with a course of progesterone.”

There is one 2012 study on the use of progesterone after mifepristone and before misoprostol. It is frequently cited by abortion opponents. But the study included only six cases and it was not, as ACOG points out, a “controlled study.” Its lead author is none other than George Delgado, the aforementioned medical director of APR.

After medical experts critiqued his study, Delgado told ThinkProgress that he has since had a 55 to 60 percent success rate with roughly 200 women. He has made similar estimates in other interviews but still, there is no peer-reviewed proof.Not only is “abortion reversal” scientifically unproven, it is not FDA-approved and possibly dangerous. As ACOG notes: “Progesterone, while generally well tolerated, can cause significant cardiovascular, nervous system and endocrine adverse reactions as well as other side effects.” (PDF)

On the other hand, medical abortion is FDA-approved and the federal agency relaxed its guidelines around mifepristone this March. Now, the FDA’s new label for the first pill specifies that it can be used with 70 days from the start of a woman’s last period and that misoprostol can be taken “at a location appropriate for the patient” rather than in a doctor’s office.

Whereas three states now require women to be told that medical abortion can be reversed, Rep. Hoffman says he simply wants Louisiana’s state health department to study the issue first before looking at a similar requirement.

“We wanted to make sure it works,” the lawmaker told WWL.

Hoffman has already authored House legislation that would ban Planned Parenthood from receiving Medicaid funding if they begin performing abortions in the state. That bill cleared the house 85-7 last month. Now, he wants to spend taxpayer dollars researching a dubious and possibly dangerous medical procedure.