NASHVILLE (AP) — A federal appeals court on Thursday quizzed the defense presented by Tennessee's attorneys of the state's sweeping abortion ban, focusing particular attention on how prohibiting the procedure as early as six weeks into pregnancy would not be a considered an unfair burden.

"Something like 80% of women have abortions after the time when normally a heartbeat is able to be detected," said Judge Karen Nelson Moore during Thursday's hearing. "If something like 80% of women can't get abortions because a heartbeat has been detected, yet they want an abortion, why isn't that a substantial obstacle to them having an abortion?"

Sarah Campbell, special assistant to Tennessee's attorney general, countered that the state's ban prohibits abortion at various cascading gestational ages. The law states that if the six-week ban is deemed unconstitutional — a time frame when most people don't know they're pregnant — then the ban would begin at various other gestational stages.

Campbell argued the state is focused on drawing a line at 15 weeks.

"(At) that point there is a growing medical consensus that an unborn child is capable of experiencing of not only having pain but perceiving pain at that point in time," she said. "The state has an interest in preventing that pain."

The plaintiffs attorney, which include Tennessee abortion providers being represented by reproductive rights groups, disputed that pain could be perceived at such an early gestational age.

"Even assuming the state's interest in fetal pain, there is no state interest sufficient to justify a ban on abortion prior to viability," said attorney Rabia Muqaddam.

The ongoing legal battle surrounding the contentious Tennessee law began last year when Republican Gov. Bill Lee signed it; the law was blocked hours later by a lower federal court.

The case is now before the 6th U.S. Circuit Court of Appeals in Cincinnati. Via livestream, the court listened to oral arguments on both sides of the case and will release their decision at a later date.

While the majority of Tennessee's abortion ban has never been enacted, the federal appeals court agreed in late November that the state could implement one portion called the "reasons bans." That section prohibits abortions because of a prenatal diagnosis of Down syndrome, as well as prohibit the procedure if it's based on the race or gender of the fetus.

The plaintiffs had argued the ban was improperly vague, claiming the law failed to provide clear guidelines for abortion providers to avoid criminal prosecution, but the court disagreed.

Currently, more than a dozen states have similar reason bans in place.

Campbell argued that it would be incredibly difficult for a prosecutor to prove that a physician knew in advance that a woman was seeking an abortion because of a Down syndrome diagnosis. The law calls for criminal penalties against doctors who violate it.

"So if it's true, as plaintiffs contend, that it's really impossible to know another person's motivations for seeking an abortion, then that's a problem for the prosecution," she said, adding that burden to prove "actual knowledge" would eliminate concerns the ban was vague.

Down syndrome is a genetic abnormality that causes developmental delays and medical conditions such as heart defects and respiratory and hearing problems.

According to the National Down Syndrome Society, about one in every 700 babies in the United States — or about 6,000 a year — is born with the condition, which results from a chromosomal irregularity.

Notably, Campbell conceded that while Down syndrome may not be a legal reason under the Tennessee law to seek out an abortion — concern over mental health deterioration following that denial would be a valid reason for providers to carry out the procedure.

"That would be our position," she said.