DES MOINES, Iowa — Republican lawmakers with control of the Iowa statehouse fast-tracked a bill early Wednesday that would ban most abortions once a fetal heartbeat is detected, usually around six weeks of pregnancy, sending what could be the nation’s most restrictive abortion legislation to the governor.

Critics say the so-called “heartbeat” bill would ban the medical procedure before some women even know they’re pregnant, and it sets the state up for a legal challenge over its constitutionality.

“How dare we think that the privacy and decisions of a woman and her medical choices are up to us to determine?” said Rep. Vicki Lensing, an Iowa City Democrat, during House floor debate that began Tuesday afternoon and stretched into the early hours of Wednesday. “I am personally offended by this bill that seems to second-guess a woman’s ability to make an unintended and difficult decision.”

The measure was passed with nearly back-to-back chamber votes along party lines, culminating in approval in the Senate chamber shortly after 2 a.m. The bill now heads to Republican Gov. Kim Reynolds, who is anti-abortion but hasn’t said publicly if she will sign it into law. Her press secretary, Brenna Smith, indicated in an email the Republican was open to signing it.

“Governor Reynolds is 100 percent pro-life and will never stop fighting for the unborn,” Smith said.

The legislation passed overnight has some exemptions, allowing abortions after a detectable heartbeat in order to save a pregnant woman’s life, and in some cases of rape and incest. Another provision prohibits some uses of fetal tissue, with exemptions for research.

Republicans at the Iowa Capitol have long sought to approve legislation that would further restrict abortion, and their flip of the state Senate chamber in the 2016 election gave them a trifecta of GOP power for the first time in nearly 20 years. Last session, they passed a bill banning most abortions after 20 weeks of pregnancy. A three-day waiting period for abortions remains on hold amid litigation.

During Tuesday night’s debate, Republicans praised the legislation.

“A baby has become something we can throw away. This bill says it’s time to change the way we think about unborn life,” said Rep. Sandy Salmon, a Janesville Republican.

If passed, the legislation could face challenges claiming it violates U.S. Supreme Court rulings, including Roe v. Wade. Some Republicans say they want the bill to abolish the landmark 1973 ruling that says women have a right to terminate pregnancies until a fetus is viable.

“I would love for the United States Supreme Court to look at this bill and have this as a vehicle to overturn Roe v. Wade,” said Sen. Jake Chapman, a Republican from Adel.

Several states have attempted to advance abortion bans in recent years. Mississippi passed a law earlier this year banning abortions after 15 weeks of pregnancy, but it’s on hold after a court challenge. A federal appeals court, whose territory includes Iowa, rejected heartbeat bills passed in 2013 in North Dakota and Arkansas. The U.S. Supreme Court then declined to review the cases.