A pair of Republican lawmakers have introduced a bill that would ban most abortions in Tennessee should the Supreme Court overturn Roe v. Wade, its landmark decision legalizing abortion.

The "Human Life Protection Act" would create one exception to the ban: when an abortion is necessary to prevent death or "substantial and irreversible impairment of major bodily function."

If enacted, the measure would make it a felony for a doctor to perform an abortion, while women seeking abortions would be exempt from prosecution.

It would be up to doctors to prove the abortion was necessary to prevent a woman's death as part of an "affirmative defense to prosecution." A physician performing an abortion would also have to prove that he or she had made a best-faith effort to deliver a live infant.

The measure, introduced by Sen. Dolores Gresham, R-Somerville, and Rep. Susan Lynn, R-Mt. Juliet, would take effect 30 days after the Supreme Court overturned Roe v. Wade in whole or part — or if an amendment to the U.S. Constitution is adopted giving states the authority to ban abortions.

“This bill will ensure Tennessee remains a national leader in preserving protections for our unborn and the women of our state," Lynn said.

The bill is a priority for Tennessee Right to Life, which advocates against abortion, and has built a large, grassroots following that was responsible for passing a constitutional amendment removing the right to an abortion from Tennessee's constitution.

"We don't know when the U.S. Supreme Court may determine to allow states to decide abortion policy, but when they do, we want to be in a position to restore full legal protections for women, girls and unborn children in Tennessee," Tennessee Right to Life President Brian Harris said.

Sen. Raumesh Akbari, D-Memphis, said lawmakers should place their efforts elsewhere.

“Access to the full range of reproductive health services is an issue that’s been settled now for decades," she said. "We should focus on proven policies that help women have safe pregnancies and healthy babies when they’re ready."

Tennessee bill could take effect if Roe overturned 'in part'

Four other states — Louisiana, Missouri, North Dakota and South Dakota — have already enacted similar laws; three states — Arkansas, Kentucky and South Carolina — are currently considering enacting a similar "trigger" law, said Elizabeth Nash, senior state issues manager with the Guttmacher Institute, which tracks abortion-related bills.

"It isn't surprising we are seeing this kind of legislation right now given what is expected to happen at the Supreme Court — the anticipation that the court will be revisiting abortion rights not in the too distant future and also the expectation that, now the court is more conservative, any decision around abortion would undermine abortion rights," Nash said.

What sets Tennessee's measure apart, Nash said, is that other states rely on the 1973 Roe v. Wade decision being overturned completely. The bill in Tennessee would be triggered if the Supreme Court overturned Roe "in part."

There are currently three abortion cases the Supreme Court could potentially use as a vehicle to alter or overturn Roe: an Indiana ban on abortion for race, gender and fetal anomaly selection, an Alabama ban on "dilation and evacuation" abortions and a Louisiana law requiring physicians performing abortions to have admitting privileges at local hospitals.

The bill is one of a half-dozen abortion-related measures introduced by Tennessee lawmakers after the legislature convened for a new session in January.

A Republican lawmaker introduced a bill that would make it a crime to perform or obtain an abortion in Tennessee after a fetal heartbeat is detected.

Other proposals would change the age that triggers the requirement that a physician report suspected sexual abuse of a minor who is seeking an abortion from under 13 years of age to under 18 years, and a proposal barring the state from awarding funding to any organization that performs abortions or provides referrals to abortion provider.

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Reach Anita Wadhwani at awadhwani@tennessean.com; 615-259-8092 or on Twitter @AnitaWadhwani.