An Iowa judge struck down Tuesday a law basing an abortion ban on a fetal heartbeat, blocking the implementation of one of the strictest abortion bans in the U.S.

"I am incredibly disappointed in today's court ruling, because I believe that if death is determined when a heart stops beating, then a beating heart indicates life," Iowa Gov. Kim Reynolds said in a statement.

Polk County District Judge Michael Huppert decided the case immediately because no facts were in dispute, the Des Moines Register said.

His nine-page ruling, issued Jan. 22, cited a 2018 Iowa Supreme Court decision striking down a 72-hour waiting period for abortion, on the grounds that "a woman's right to decide whether to terminate a pregnancy is a fundamental right under the Iowa Constitution." He said the law's defenders didn't identify a compelling state interest to bar abortions based on when a fetal heartbeat is detected.

The 2018 law would have required any women seeking an abortion to undergo an ultrasound to determine whether a fetal heartbeat can be detected, a milestone usually detected around the sixth week of pregnancy. The legislation made some exceptions for pregnancies conceived through rape or incest, as well as fetal abnormality, or if a doctor determines that a woman's life is in danger.

Iowa Attorney General Tom Miller declined to defend the law. Lawyers from the Chicago-based Thomas More Society argued on its behalf in court at no expense to taxpayers.

They previously argued against the claim that facts were not in dispute, saying that the law is not a blanket ban, but a tailored regulation.

Maggie DeWitte, executive director of Iowans for Life, voiced hope that the ruling would be overturned on appeal. She said it was a "travesty of justice" that the judge would not allow the case "to go before a fair trial."

The bill passed the Iowa House of Representatives by a vote of 51-46 and passed the Senate by a vote of 27-19.

The law did not take effect pending the legal challenge from the American Civil Liberties Union of Iowa, the abortion provider Planned Parenthood of the Heartland and the Iowa City-based Emma Goldman Clinic, which also performs abortions.

Rita Bettis Austen, legal director for ACLU of Iowa, said the ruling was "essential for the rights and safety of women in Iowa." She said the 2018 state supreme court decision cited by Huppert "recognized the fundamental right to a safe and legal abortion for Iowa women, which cannot be legislated away."

Legal scholars said appealing a decision based on the Iowa constitution would face difficulty because the U.S. Supreme Court has little jurisdiction over issues affecting the state constitution.

The lawsuit argued that the law violated the due process rights of women, as well as their rights to liberty, safety and happiness and their rights to equal protection under the state constitution, the Des Moines Register reported.

Under current law, abortion is legal in Iowa until the 20th week of pregnancy. The new law struck down on Tuesday was among the strongest abortion regulations in the country.

State Sen. Janet Petersen of Des Moines, the Democratic minority leader, said the law was "extreme" and should have been overturned "because it restricted the freedom of Iowa women and girls to care for their bodies, and it forced motherhood on them."

Last year the Ohio legislature passed a similar bill banning abortion based on fetal heartbeat, but failed to override Gov. John Kasich veto. Kasich's successor, also a Republican, has voiced support for the bill.

(Story continues below)

The first heartbeat-based abortion ban was passed in 2013 by the Arkansas legislature, which also voted to override a governor's veto of the bill.. The U.S. Court of Appeals for the Eighth Circuit ruled it was unconstitutional and the U.S. Supreme Court declined to hear an appeal.

South Carolina, Kentucky, and Missouri could consider heartbeat abortion bans this year.

The law also banned all persons from knowingly acquiring, providing, transferring, or using fetal remains in Iowa. This did not apply to medical diagnostic samples, or forensic investigations, or to fetal body parts donated for medical research after a miscarriage or stillbirth. It is unclear whether those provisions still apply.

Iowa Gov. Kim Reynolds signed the bill into law May 4, 2018.

"I believe that all innocent life is precious and sacred, and as governor, I pledged to do everything in my power to protect it. That is what I am doing today," she said at the time. Reynolds said she felt it was "immoral to stop an innocent beating heart," as well as "sickening to sell fetal body parts."

The Republican governor acknowledged the near certainty that the law would face court challenges, claiming her actions were "bigger than just a law," and that she will not back down.

Catholic bishops of the state had voiced qualified support for the bill's intentions.

"We support the life-giving intent of the provisions in the bill and we want to do everything we can to support that," Bishop Walker Nickless of Sioux City, Iowa, told CNA in a May 2018 interview before the bill was signed into law.

He voiced hope that the bill could halt some trafficking of fetal body parts following an abortion.

Iowa's bishops recognized that some provisions of the bill might not withstand judicial scrutiny.

Bishop Nickless added that Catholics might disagree about the strategy of supporting legislation that could be overturned by courts. He encouraged creative pro-life advocacy, saying Catholics should discern such questions carefully. He said the message of the state's bishops had been: "If you're a Catholic and your conscience tells you to support this, please do."

Nickless reaffirmed that the Catholic Church supports the health and rights of all women, including those in the womb. "If we are talking about women we need to make sure we are talking about unborn females as well, and protecting them," he said.