LINCOLN–(KFOR/AP Apr. 27)–Second round of debate started late Thursday morning in the Nebraska Legislature on a bill that would ban abortion once cardiac activity can be detected in an embryo, which generally occurs around the sixth week of pregnancy and before most women know they’re pregnant.

Supporters advanced LB 626 from the first round of debate earlier this month with only a one-vote margin to break a filibuster. The bill must survive Thursday’s debate and a final round to pass.  Lawmakers began debate on an amendment introduced by a Republican co-signer and Ralston Senator Merv Riepe that would extend the proposed ban to 12 weeks.

The amendment and reports of support for it by some lawmakers who voted for the bill earlier this month could signal that a ban set very early in pregnancy may face pushback even from those who want further abortion restrictions.

The bill makes specific exceptions for ectopic pregnancies, IVF procedures, and allows for the removal of a fetus that has died in the womb. It also does not ascribe criminal penalties to either women who receive or doctors who perform abortions. Instead, it would subject doctors who perform abortions in violation of the measure to professional discipline, which could include losing their medical licenses.

The close divide played heavily in the defeat last year of a so-called trigger bill that would have automatically banned nearly all abortions in the state, even those resulting from rape and incest, as soon as the U.S. Supreme Court overturned Roe v. Wade, which had guaranteed the right to abortion nationwide for nearly five decades. That bill fell two votes short.

In the vote to advance the abortion bill earlier this year, Omaha Senator Mike McDonnell, a Democrat, voted with Republicans. His reason, he said, is that he is a devout Roman Catholic who has always campaigned as an anti-abortion candidate.