On Tuesday, the House of Representatives will vote on the Pain-Capable Unborn Child Protection Act, a measure spearheaded by Reps. Trent Franks (R-AZ) and Marsha Blackburn (R-TN) that would cut off legal access to abortion services at 20 weeks after fertilization. It represents the most restrictive abortion bill to come to a vote in either chamber over the past decade. Here’s what you need to know about this attack on women’s reproductive rights — and how it fits into a broader, coordinated nationwide campaign to slowly chip away at abortion access:

It’s based on the scientifically-disputed theory that fetuses can feel pain before the third trimester of pregnancy.

So-called “fetal pain” measures are based on junk science that represents a minority position among medical professionals. Most doctors don’t believe that fetuses can feel pain until much later in pregnancy, after the point of viability (generally considered to be around 24 weeks), and scientific research has repeatedly confirmed this position. Nevertheless, abortion opponents have successfully stoked emotional outrage surrounding later-term abortion — particularly following the high-profile murder trial of illegal abortion provider Kermit Gosnell — by twisting the facts to make it appear that these abortions are always barbaric procedures.

It has sparked more controversy over Republicans’ attitudes toward rape.

The original version of Franks’ legislation did not include an exception for victims of rape or incest. Defending the lack of an exception in these cases, the Arizona congressman last week claimed that “the incidence of rape resulting in pregnancy are very low.” Franks is just the latest Republican to make an offensive comment about rape victims, and his comments inspired comparisons to former Rep. Todd Akin’s (R-MO) infamous assertion that women don’t often get pregnant from “legitimate rape” because the body “has ways of shutting that whole thing down.” Following the controversy that erupted from his statements, Franks revised the legislation at the last minute to include an exemption for survivors of rape and incest — but only if rape victims first report the sexual crime to the police, and if incest victims are minors.

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