* Republican-backed bill goes to governor to sign into law
* Anti-abortion activists push measures in U.S. states
* A 1973 Supreme Court ruling legalized abortion in U.S.
By Laura Zuckerman
SALMON, Idaho, April 5 (Reuters) - The Republican-dominated Idaho legislature gave final approval on Tuesday to a measure to outlaw abortions after 20 weeks of pregnancy and subject abortion providers to criminal prosecution and civil lawsuits.
The state House of Representatives voted 54-14 to pass the legislation, which earlier cleared the state Senate, and sent it to Republican Governor Butch Otter, who is expected to sign it into law.
The legislation is linked to disputed medical research suggesting that a human fetus can feel pain at 20 weeks of gestation and is modeled on a 2010 Nebraska law that has yet to face a legal challenge.
The Idaho bill also is similar to one approved by the Kansas legislature last month and to measures proposed by lawmakers in more than a dozen other U.S. states.
Anti-abortion activists are working at the state level to tighten restrictions on abortion after sweeping Republican gains in state elections last year.
The effort has found favor in states such as Idaho, Kansas and North Dakota, with Republican governors and Republican-controlled legislatures.
The Idaho measure would make it a felony to perform an abortion after 20 weeks of gestation unless it can be proven that the pregnancy endangers the woman's life.
It also would open violators to lawsuits by the woman and the father and allow spouses, relatives and others to file legal injunctions against physicians who violate the law.
Backers of the measure said it is needed even though state figures show that only about 1 percent of abortions in Idaho in 2009 involved pregnancies at 20 weeks or more.
"We want to use legislation in as many ways as possible to talk about the humanity of the unborn child," Mary Spaulding Balch, director of state legislation for the anti-abortion group National Right to Life Committee, said in a recent interview.
Abortion rights activists say the state measures represent attacks on the U.S. Supreme Court's landmark 1973 Roe v. Wade ruling legalizing abortion in the United States.
"Idaho legislators have clearly abandoned their promise to focus on jobs and the economy to advance a ban that directly interferes in a woman's relationship with her doctor," Nancy Keegan, president of NARAL Pro-Choice America, an abortion rights lobbying group, said in a statement.
(Editing by Dan Whitcomb and Greg McCune)