The governor of Texas has signed a law banning abortion from as early as six weeks - before most women know they are pregnant.
Governor Greg Abbott signed the legislation at a ceremony on Wednesday.
It bans abortions after the detection of what anti-abortion campaigners call a foetal heartbeat, something medical authorities say is misleading.
The law is also unique in giving any individual the right to sue doctors who perform the procedure past this point.
Doctors and women's rights groups have heavily criticised the law, which will take effect in September if it is not stopped by a court.
Texas is the latest and largest US state to pass abortion restrictions.
It comes just days after the US Supreme Court agreed to hear a case which could upend the nationwide legal right to abortion, laid out in the landmark 1973 Roe v Wade ruling. A ruling could give individual states greater powers to restrict abortions.
What does the Texas abortion law say?
"Our creator endowed us with the right to life, and yet millions of children lose their right to life every year because of abortion," Governor Abbott said at the ceremony, which was broadcast live on Facebook. "In Texas we work to save those lives."
The heartbeat bill is now LAW in the Lone Star State.— Greg Abbott (@GregAbbott_TX) May 19, 2021
This bill ensures the life of every unborn child with a heartbeat will be saved from the ravages of abortion.
Thank you @SenBryanHughes, @ShelbySlawson, & #txlege for fighting for the lives of the unborn in Texas. pic.twitter.com/aolhUKM9tv
Unlike in other states, the Texas law does not let state officials enforce the ban. Anyone inside or outside the state instead now has the power to sue abortion providers - or anyone who could have helped a person to get the procedure - after the limit. They can seek up to $10,000 (£7,061) in damages per defendant.
The Texas Tribune reports that supporters of the bill hope this novel provision will trip up legal challenges to the legislation, as without state officials enforcing the ban, there will be nobody for pro-women's rights groups to sue.
It also allows abortions in the case of a medical emergency, but not for pregnancies resulting from rape or incest.
Close to a dozen states in the US have passed similar laws based on the "foetal heartbeat" provision. But the American College of Obstetricians and Gynaecologists says the name is misleading, and that what is being detected is "a portion of the foetal tissue that will become the heart as the embryo develops".
In a statement on Wednesday, Planned Parenthood Action Fund President Alexis McGill Johnson said it was "appalling that in defiance of public opinion and public health, state politicians remain committed to controlling our bodies."
"Access to abortion has never been more at risk — and we're going to fight back like hell," she tweeted.
And an open letter signed by 200 doctors earlier this month said they were "deeply concerned" by the bill, and how it empowers individuals to sue healthcare providers.
"These bills create a chilling effect that might prevent physicians from providing information on all pregnancy options to patients out of fear of being sued," it read. "The Texas legislature has no right to cause this type of grievous harm to Texas physicians or the people we serve."