Dr. Mitchell Creinin never expected to be in the position of investigating a treatment he doesn't think works. And yet, Creinin will be spending the next year or so using a research grant from the Society of Family Planning to put to the test a treatment he sees as dubious - one that recently has gained traction, mostly via the Internet, among groups that oppose abortion. They call it "abortion pill reversal."

The technique - a series of oral or injected doses of the hormone progesterone given over the course of several days - arose outside the usual avenues of scientific testing, says Creinin, a medical researcher and professor at the University of California, Davis. 

Creinin, an OB-GYN, has spent the bulk of his career in family planning research. He has studied topics ranging from different treatments for miscarriage to how women choose birth control methods.

Performing abortions, he says, has always been a part of his practice and philosophy. "I need to provide these services to help women," Creinin says. Proponents of "abortion pill reversal" say it can stop a medication-based abortion in the first trimester, if the progesterone is administered in time. But Creinin says the progesterone treatments are ineffective at best in halting an abortion that has already begun. And, Creinin says, promotion of the treatment can be potentially harmful by giving pregnant women misleading information that an abortion can be undone.

Though critics of abortion pill reversal say the term is an unproven misnomer, it has been such a compelling phrase that it's already been written into the laws of a number of states.Legislators in Arkansas, Idaho, South Dakota, and Utah have made it a legal requirement in recent years that doctors who provide medical abortions must tell their patients that "reversal" is an option, although they are not prevented from also telling patients if they think the treatment doesn't work.

Medical researchers such as Creinin and the American College of Obstetrics and Gynecology are concerned by that trend. "You create a law based on no science - absolutely zero science," Creinin says. Proponents of the technique say they do have evidence. But it's anecdotal, Creinin says, or comes from studies that lack rigorous controls. It's time, Creinin says, for a formal study that can be definitive."I want to own that," he says. 

One of Delgado's most outspoken critics, Dr. Daniel Grossman, an OB-GYN at the University of California, San Francisco, says all of the published studies supporting this use of progesterone have been marred by methodological flaws that inflate the "success rate" of the reversal treatment. Last October, Grossman and Kari White, a sociologist at the University of Alabama, Birmingham who studies family planning issues, wrote an editorial in the New England Journal of Medicine criticizing Delgado's research methodology, saying he used flawed statistics and didn't set rigorous criteria for the characteristics patients had to fulfill to be included in the study.

"A systematic review we coauthored in 2015 found no evidence that pregnancy continuation was more likely after treatment with progesterone as compared with expectant management among women who had taken mifepristone," they wrote.

"I think there's a big bias against abortion pill reversal," Delgado says in response. "ACOG typifies that bias by coming out with strong statements. ... This is a new science, but we have a substantial amount of data, and it's been proven to be safe." 

The critics haven't slowed Delgado's supporters.