Abortion has been outlawed in the US state of Iowa for women about six weeks pregnant.
Iowa Governor Kim Reynolds has signed into law a bill outlawing abortion after a fetal heartbeat is detected, which often occurs at six weeks and before a woman knows she is pregnant.
The measure is the most restrictive abortion ban in the United States.
"I understand and I anticipate that this will likely be challenged in court, and that courts may even put a hold on the law until it reaches the Supreme Court," said Reynolds while singing the bill, surrounded by children.
"However, this is bigger than just a law; this is about life. I'm not going to back down from who I am or what I believe in."
Chants from protesters were audible in the room where Reynolds signed the bill, in a ceremony that was broadcast live.
State senators who backed the measure said earlier this week that they were aiming to challenge the US Supreme Court's landmark Roe v. Wade decision that established that women had a constitutional right to abortion.
Abortion opponents hoping to land the issue back in front of the nation's top court believe the 5-4 conservative majority could sharply curtail abortion access or ban it outright.
At a rally in Des Moines on Friday officials of Planned Parenthood, the women's healthcare group and backer of abortion rights, said they would file a lawsuit to block the law.
"I am here to tell Governor Reynolds, we will see you in court," Planned Parenthood of the Heartland president Suzanna de Baca said.
"We will challenge this law with absolutely everything we have on behalf of our patients, on behalf of your rights, because Iowa will not go back."
Mississippi's Republican governor in signed into law a bill banning abortion after 15 weeks with some exceptions in March, sparking an immediate court challenge by abortion rights' advocates.
A similar court challenge is under way in Kentucky, which in April enacted a ban on a common abortion procedure from the 11th week of pregnancy.