On the same day that Texas Governor Rick Perry signed a controversial abortion omnibus bill into law, Republican legislators in the state introduced yet another anti-abortion measure, this time looking to ban abortions after 6 weeks. And while it seems very unlikely at this point that the bill will make it through the state's legislative process by July 31, the end of the current special legislative session in Texas, the timing is still drawing a decent bit of attention.

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There's only one state in the U.S. with an abortion ban after 6 weeks: North Dakota. And that law is being challenged in the courts as unconstitutional. The 6-week bans, like the one proposed in Texas, rely upon the detection of a fetal heartbeat by a doctor. Arguing that a fetal heartbeat is "a key medical predictor that an unborn child will reach live birth," the Texas bill, HB59, would require doctors to determine whether a fetal heartbeat exists before legally performing an abortion. Fetal heartbeats typically register at around 6 weeks, meaning that the bill would effectively make that the cut off for the procedure.

Like Texas's new abortion law, which, among other things, bans abortions after 20 weeks, the bill directly challenges the current constitutional standard for determining the legality of the procedure. Based on the Roe v. Wade decision, that standard is fetal "viability," which state laws usually set at about 24 weeks. The new 20-week law, by comparison, uses "fetal pain," a scientifically challenged notion that fetuses feel pain at that point, to set a new legal limit to abortions.

Normally, a just-filed bill like this doesn't really warrant a look — it's not even yet recommended to a committee, and the Republicans who support it would have to really hustle to get it through the entire legislative process by the end of the month (especially given that they're tentatively on break until July 25). But after a weeks-long fight in Texas to stop a the new abortion laws, HB59 is bound to get some attention.

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Plus, the unlikelihood that HB59 will become Texas law doesn't mean that the state is free from future attempts to reduce the time window for legal abortions, or to eliminate the legality of the procedure altogether. As anti-abortion opponents have noted, later-term abortions are politically unpopular, which makes something like a 20-week abortion ban, from an anti-abortion perspective, an easier, incremental sell to the American public. But the procedure isn't really representative of the vast majorities of abortions performed in the U.S.: abortions after 20 weeks also very rare. Then again, anti-abortion legislators, as is vividly apparent from the rhetoric used in defense of the bills, are by no means looking to end the abortion fight at a 20-week ban. That's where "fetal pain" comes in: by changing the constitutional standard to a scientifically dubious set of claims, abortion opponents would open up a giant opportunity to push the time limit back to eight weeks, based on the research the fetal pain standard relies on. At Slate, Will Saletan flagged why, while writing about a similar 20-week ban passed in the House of Representatives:

Rep. Marsha Blackburn, R-Tenn., managed the debate for pro-lifers. “We know that at eight weeks, babies feel pain,” she told her colleagues. Eight weeks? What happened to 20? The answer is that fetal pain is ambiguous. You can stretch the definition to justify banning abortions much earlier than 20 weeks. Maureen Condic, the pro-lifers’ go-to neuroscientist, laid out the timeline at a recent House subcommittee hearing. Here’s the text of her presentation slide (shown just before the 1:15 mark on thehearing video): Milestones in pain development 4 weeks: Basic structures of nervous system established. 4 weeks: Earliest neurons in the cortex are born. 7 weeks: Synapse formation begins in cortex. 8-10 weeks: Spinal circuitry for pain detection is established. The fetus is capable of reacting to painful sensory input. 8-10 weeks: Subcortico-frontal pathways established. 12-18 weeks: Spino-thalamic pathways established. The fetus is capable of mature pain perception. 22-24 weeks: Long-range cortical projections form.

Meanwhile, Texas's new abortion law won't even go into effect by September, and it's possible that the bill, like similar bills passed in other states, could become mired in litigation by that point.