Since Nebraska first jump-started the trend back in 2010, close to a dozen state legislatures across the country have passed laws banning abortion at 20 weeks. Most of these restrictions are given grave-sounding titles like the “Pain-Capable Unborn Child Protection Act,” or some near-identical riff on the words “fetal,” “pain” and “protection.” All of them, no matter what they’re called, rest on the stated premise that a fetus can experience pain at 20 weeks, and that this is a sufficient justification to ban all abortions after this gestational stage.

But “fetal pain” in the popular discourse is a nebulous concept, one that lawmakers like Jodie Laubenberg, Trent Franks and others haven’t much bothered to define or help ground in available medical evidence.

Probably because there really isn’t any. The limited research used to support such claims has been refuted as pseudoscience by both the Journal of the American Medical Association and the British Royal College of Obstetricians and Gynecologists. (Not to mention smaller studies from researchers at Harvard University, University College London and elsewhere.)

“We know a lot about embryology [in the field]. The way that a fetus grows and develops hasn’t changed and never will,” Dr. Anne Davis, a second-trimester abortion provider, associate professor of clinical obstetrics and gynecology at Columbia University Medical Center, and consulting medical director at Physicians for Reproductive Health, told Salon. “And what we know in terms of the brain and the nervous system in a fetus is that the part of the brain that perceives pain is not connected to the part of the body that receives pain signals until about 26 weeks from the last menstrual period, which is about 24 weeks from conception.”

Because the neural structures necessary to feel pain have not yet developed, any observable responses to stimuli at this gestational stage — like the fetal “flinching” during an amniocentesis — are reflexive, not experiential. Which is to say, the fetus at 20 weeks can’t actually feel anything at all. Which is to say, the fundamental justification for these laws is a really big, really popular lie.

“That’s just where the science is. You can have an opinion about that, but it doesn’t change the information,” Davis says. “Science is not going to get the brain to connect faster.” (Neither, it should be noted, will the hoping, wishing or foot-stomping of politicians like Marco Rubio and his anti-choice contemporaries.)