Sarah Kliff's piece here isn't phrased this way, but that's the net impact of the state legislature's veto override on a bill outlawing all abortions after 12 weeks of gestation, by defining fetal "viability" as "when the fetus has a heartbeat", a definition which has no basis in the science of anything.
Let's set aside entirely the fact that a decent number of pregnant women don't even confirm that they're pregnant before week 12. The most accurate form of prenatal screening for birth defects or genetic diseases can't be completed until week 14 or 15. But even the best screening still has a 5-10% false positive rate. Given the rates, this means roughly 5 out of every 6 fetuses that have a positive screen do not actually have any defect or disease. So if the it comes back positive, you have to perform an invasive followup test, usually an amniocentesis or CVS, that has something much closer to perfect accuracy. Amniocentesis also cannot be performed until week 15. After that, you have to wait for the test results, and if those come back positive, you have to make a decision about the quality of life your family and the child would have. Some of the defects that are screened for, such as trisonomy 18 (that's the genetic defect that ails Rick Santorum's daughter), result in extremely shortened lifespans or extremely low quality of life. The Arkansas bill would effectively require expectant mothers whose fetus has a defect like this to carry it to term, irrespective of their family, financial, and mental tolerance for the strain this would put on them.
Under current Supreme Court jurisprudence, the Arkansas bill is unconstitutional on its face. The state legislature is not empowered to define viability by judicial fiat, and even if they were, a demand from the government that women carry a pregnancy even if the fetus would barely survive outside the womb to term almost certainly violates the "undue burden" test, if those words are to have any meaning at all. But to enact such a law under any circumstances shows an utter callousness to the on-the-ground realities of childbearing & childrearing decisions.