The Senate passed the Unborn Victims of Violence Act (search) on Thursday, following House passage last month of an identical bill that would make it a crime to harm a fetus during a violent federal crime.
But the bill, meant to further penalize someone who attacks a pregnant woman, has energized partisans on both sides of the abortion issue.
"They want to make this bill about a woman's right. What on earth does this have to do with a woman's right to choose? Nothing," said Sen. Barbara Boxer, D-Calif.
The bill, which will now be sent to President Bush, is also called "Laci and Conner's law" after Laci Peterson (search), the murdered California woman whose unborn son was to be named Conner. The vote has become a top priority of anti-abortion organizations and abortion-rights groups.
Bush issued a statement late Thursday praising the Senate's action.
"Pregnant women who have been harmed by violence, and their families, know that there are two victims -- the mother and the unborn child -- and both victims should be protected by federal law. I look forward to signing this important legislation into law," he said.
The bill states that an assailant who attacks a pregnant woman while committing a violent federal crime can be prosecuted for separate offenses against both the woman and her unborn child, "a member of the species homo sapiens, at any stage of development, who is carried in the womb."
"This bill recognizes that there are two victims. There is the victim, the mother who was assaulted, and there is the victim, the unborn child: He was either injured or killed," said Sen. Mike DeWine, R-Ohio.
Tracy Marciniak, who was days away from giving birth when the father of the child brutally beat her, traveled to Capitol Hill to support the bill.
"My son was five days from full-term, and for them to tell me my son was nothing, it's just wrong," Marciniak said. "Where were my child's rights when he was ripped from my womb and killed, and I was told he was nothing?"
The Senate cleared the way for passage of the bill by narrowly defeating an amendment, 50-49, that would have given more comfort to abortion rights lawmakers. The measure would have increased penalties on assailants but maintained that an attack on a pregnant victim was a single-victim crime.
Sen. Dianne Feinstein, D-Calif., who authored the amendment, feared the implications of the bill. "If this result is incorporated, it will be the first step in removing a woman's right to choice," she said. Feinstein said it could also chill embryonic stem cell research.
Supporters of the legislation countered that it is not about abortion, but about protecting pregnant women.
"Most of us, large percentages of us, want to whack the person who did it as hard as we can, and we don't want to get into the debate about abortion," said Sen. Lindsey Graham, R-S.C.
Sen. Rick Santorum, R-Pa., said the Feinstein amendment was "all about denying the humanity of the child" and that abortion rights proponents were trying to defeat the bill "to protect this right that is not even at stake here today."
The Senate also debated an amendment by Sen. Patty Murray, D-Wash., that would have required employers to give unpaid leave, and states to pay unemployment benefits, to women when they or family members are victims of domestic or sexual violence.
But the amendment was defeated, leaving the Senate bill to mirror the House bill, which means the the legislation could go directly to the president for his signature without requiring a conference between the chambers.
The Senate bill covers 68 federal violent crimes, including drug-related shootings, violence at an international airport, terrorist attacks, crimes on a military base and threats against a witness in a federal proceeding.
It specifically excludes prosecution of legally performed abortions — a fact supporters cite in arguing that the bill would not undermine the 1973 Roe v. Wade (search) decision affirming a woman's right to end a pregnancy.
"The criminals who commit these crimes are not committing abortions," said Douglas Johnson, legislative director of the National Right to Life Committee (search). "They are depriving these unborn children of the right to life. It's a separate issue related to the right to life."
Groups on both sides of the abortion issue lobbied hard on the legislation. The Christian Coalition of America (search) said votes for either the Murray or Feinstein amendments would be regarded as negative votes on its annual congressional scorecard of lawmakers.
On the other side, NARAL Pro-Choice America (search) delivered petitions to senators urging defeat of the bill because the group said it would allow judges to rule that humans at any stage of development deserve protection, even when that protection trumps a woman's interest in ending a pregnancy.
"This would be the first time in federal law that an embryo or fetus is recognized as a separate and distinct person under the law, separate from the woman," said NARAL president Kate Michelman. "Much of this is preparing for the day the Supreme Court has a majority that will overrule Roe v. Wade."
Twenty-nine states already have unborn victims laws.
Fox News' Peter Brownfeld and Mike Emanuel and The Associated Press contributed to this report.