"However well intentioned, I also believe this bill would likely have very grave unintended negative consequences," Grant said.

It could give license to restrain a woman going to a provider for an abortion, she said. It could authorize and protect vigilantes.

Alan Peterson, representing ACLU of Nebraska, said if the drafters of the bill wanted it limited to the pregnant woman defending her unborn baby, they should have written it that way.

"Let's not pull out the ace of spades, the right to kill, as an answer to these tough problems," Peterson said. "The choice of violence which we're talking about here ought to be the very last."

Suzanne Gage, state director of Americans United for Life, the organization that drafted the model legislation for the bill, said Oklahoma and Missouri have enacted similar legislation.

But this bill is broader than Oklahoma's, said Omaha Sen. Brenda Council, and gives any third person the right to use force to protect an unborn child.

Studies have shown, Gage said, that violence and abuse are often higher during pregnancy. Every year, 300,000 pregnant women in the United States experience some kind of violence involving an intimate partner.