For the second time in two years, the House voted Wednesday to pass legislation that would ban almost all abortions 20 weeks after fertilization. The bill, called the Pain-Capable Unborn Child Protection Act, claims that “an unborn child is capable of experiencing pain at least by 20 weeks after fertilization,” though medical evidence does not support this.

Of course, the bill is not really about scientific findings of any sort. It is simply another attempt by conservative Republicans to undercut women’s constitutionally protected reproductive rights. A 20-week abortion ban would be a restriction before fetal viability that violates the Supreme Court’s ruling in Roe v. Wade.

The House passed a 20-week ban in 2013, but it never received a vote in the Senate. House Republicans had planned to vote on a 20-week ban again this January, but that was stalled when some Republican members objected to the bill’s language prohibiting rape victims from getting an abortion unless they had reported their rape to the police.

The measure gained momentum after The New England Journal of Medicine published a study indicating that a tiny number of babies born at 22 weeks can survive if given intensive medical treatment. Representative Diane Black of Tennessee, one of the bill’s sponsors, released a statement last Friday saying, “Science tells us that, after 20 weeks, babies can feel pain and are increasingly able to live outside the womb.”

The modified bill now allows rape victims to obtain an abortion if they’ve received counseling or medical care at least 48 hours before the procedure. It does not make an exception for the health of the mother, as current law requires. It permits an abortion after 20 weeks only if the mother’s life is in danger, which could mean a woman with health problems would have to wait until her pregnancy threatened her life.

The bill also lacks an exception for fetal abnormalities, some of which are detectable only late in a pregnancy. The measure is unlikely to pass the Senate. If it does, the White House has made it clear that President Obama will veto it.

The increasingly onerous restrictions imposed on abortion at the state level may actually be causing some women to delay their procedures into the second trimester and beyond.

One 2013 study found that women who sought abortions after 20 weeks were more than twice as likely as women who sought first-trimester procedures to report that difficulty traveling to a clinic delayed them. They were also more than twice as likely to be delayed by problems with insurance coverage.

Making it hard to get an abortion early in a pregnancy — by restricting the use of health insurance for abortion, closing clinics and mandating waiting periods — and then banning the procedure after 20 weeks would essentially prohibit abortion for those with limited resources. This, of course, is what many Republicans in Congress want, but it would be disastrous for American women and families, especially those who cannot afford to travel long distances or pay for medical procedures out-of-pocket.