Advocates of the bill call the banned procedure "partial birth abortion," and say it is a brutal and inhumane way to end the life of an unborn fetus.
Opponents of the legislation say it prohibits established medical procedures that should be legal in cases where a mother's life or health is threatened.
Three weeks ago the House passed the bill 281-142. Tuesday's vote approved a House-Senate conference committee's version of the bill, readying it for the White House. President Bush has voiced support for the legislation and observers say he is likely to sign it into law.
Former President Clinton twice vetoed similar bills because he said they lacked appropriate protection for mothers.
Opponents of the bill have said they will challenge it in court, and legal experts have said the debate could end up before the Supreme Court. In 2000, the high court struck down a Nebraska law that banned the procedure because the court said it was too vague, and did not specify the exact type of procedure it sought to ban.
The bill's sponsor, Sen. Rick Santorum (R-Pa.), expressed confidence that the legislation will stand up to legal challenges.
"We believe that this bill is constitutionally sound and obviously very, very necessary in terms of who we are as a society," Santorum said.
Democrats, including Sen. Frank Lautenberg of New Jersey, said they were confident courts would overturn the law. "This bill won't pass the constitutional test," Lautenberg said.
The bill sparked an emotional debate on the Senate floor. Opponents said that "partial birth abortion" is not a medical term and that the bill could be interpreted as a ban on different types of procedures.
Santorum argued that the term does apply to a specific procedure, which the bill defines, and that the term appears in Webster's Medical Dictionary.
Sen. Barbara Boxer (D-Calif.) said "partial birth abortion" is a "made-up term to inflame passions." Boxer further said Democrats were willing to ban "all late-term abortions" if Republicans had agreed to life and health protections for mothers. "They don't trust women," Boxer said. She also said the procedure targeted in the bill could save the life of a mother or prevent serious complications and injury, including paralysis.
Republicans, including Sen. John Ensign (R-Nev.), said the bill does include a clause that protects the life of a mother, and medical experts have concluded that the procedure is never necessary to protect a mother's health.
Democrats disputed those statements and cited other medical experts who said the procedure has been done to protect the mother's health and that decisions about the procedure should be left up to the mothers and doctors.
Much of the debate centered on the rights of women and the rights of the unborn.
"Partial birth abortion inflicts pain and suffering on an unborn child," said Sen. Jeff Sessions (R-Ala.). Sessions called the procedure "absolutely unnecessary," adding that "almost all partial birth abortion performed in America are elective." Sessions called the procedure "infanticide."
Lautenberg called the law "an attempt to regulate people's behavior." He said a woman should have "the right to make a decision about her health in concert with her doctor." Lautenberg called the Senate a "male-igarchy" and a "big boy's club" and asked his opponents why no female senators had come to the floor in the morning session to defend the bill.
"A woman's right to choose is in greater danger now than it has been since the Supreme Court decided Roe versus Wade 30 years ago," Lautenberg said. He further said the bill's "sponsors have repeatedly resisted attempts to provide a health exception."
Sen. Sam Brownback (R-Kan.) said the bill would protect the rights of the unborn. "Is it a person or is it property?" asked Brownback, referring to a fetus and relating the abortion controversy to slavery. "We are on the same debate," he said. "If it is property it can be disposed of as the owner sees fit. If it is a person it has rights."
Senators from both sides of the aisle cited public polls supporting their position.