However, this specific turning point—fetal pain at 20 weeks—has very little consensus among modern doctors: Dozens of studies have yielded pain estimates ranging from 16 to 30 weeks, and the American Congress of Obstetricians and Gynecologists has said it’s unlikely pain is felt before 29 weeks.

On the basis of this uncertain science rests one of the most comprehensive rollbacks of abortion rights in decades. It’s also a sign of the major gains the pro-life movement has made by emphasizing the agony that fetuses might feel, rather than what the movement sees as their God-given right to be born.

***

Today’s fetal pain legislation represents somewhat of a schism in the pro-life community.

In a number of court cases, beginning with Roe v. Wade in 1973, the Supreme Court ruled that states may not prohibit abortions necessary to preserve the life or health of the mother, regardless of the age of the fetus, with “health” encompassing both mental and physical health. And for no reason can states ban abortion before viability, the time, determined on a case-by-case basis, when the fetus can survive outside the womb. The medical consensus is that viability occurs at between 24 weeks and 26 weeks.

In the early 1980s, American Evangelical Christians began to coalesce around the idea that life begins at conception, but the pro-life movement’s early attempts at a constitutional amendment banning all abortion were unsuccessful.

Pro-lifers were then faced with a choice: Should they keep trying to outlaw all abortions, or simply push to make the procedure increasingly rare through piecemeal laws at the state level?

“Are you gonna go for these very broad kinds of restrictions on abortion at the federal level,” said Glen Halva-Neubauer, a political scientist at Furman University who specializes in the abortion debate. “Or were you going to attempt to take these sort of regulatory approaches?”

The more pragmatic set found early on that abstract arguments about the sanctity of life didn’t resonate as well with lay Evangelicals as did vivid descriptions of the abortion process. The 1984 video The Silent Scream, produced by the NRLC, purported to show a sonogram of a first-trimester abortion in which the fetus opened its mouth in what the narrator said was a wounded cry.

“The Silent Scream tried to elicit a sense of disgust at the prospect of the fetus being in pain during the procedure,” said Jonathan Dudley, a medical resident at Johns Hopkins who studied the anti-abortion movement at Yale Divinity School. “The idea that pain would give fetuses value is closer to a liberal worldview. They see it as more of a middle-ground position.”

From there, anti-abortion messaging focused heavily dismembered fetuses, the bloody abortion process, or the idea of fetuses being tortured to death.