Millions of women in the US will lose the constitutional right to abortion, after the Supreme Court overturned its 50-year-old Roe v Wade decision.
The judgement paves the way for individual states to ban the procedure.
Half are expected to introduce new restrictions or bans. Thirteen have already passed so-called trigger laws to automatically outlaw abortion.
President Joe Biden described it as “a tragic error” and urged states to enact laws to allow the procedure.
After the Supreme Court ruling, abortion access is expected to be cut off for about 36 million women of reproductive age, according to research from Planned Parenthood, a healthcare organisation that provides abortions.
Demonstrators from both sides had gathered outside the court, with police keeping them apart.
One anti-abortion activist told the BBC she was “elated” as her side cheered the decision. “It’s not enough just to make this the law of the land. To be pro-life is to make [abortion] unthinkable,” she said.
Across the divide, pro-choice supporters decried the decision as “illegitimate” and even a form of “fascism”.
The BBC’s Samantha Granville, reporting from an abortion clinic in Little Rock, Arkansas, said that as the ruling was posted, doors to the patient area were shut and the sound of distant sobbing could be heard before she was asked to leave. The state is one of those subject to a trigger law.
Anti-abortion activists celebrated the announcement outside the Supreme Court
The landmark 1973 Roe v Wade case saw the Supreme Court rule by a vote of seven to two that a woman’s right to terminate her pregnancy was protected by the US constitution.
The ruling gave American women an absolute right to an abortion in the first three months (trimester) of pregnancy, but allowed for restrictions in the second trimester and for prohibitions in the third.
But in the decades since, anti-abortion rulings have gradually pared back access in more than a dozen states.
In its current session, the Supreme Court had been considering a case, Dobbs v Jackson Women’s Health Organization, that challenged Mississippi’s ban on abortion after 15 weeks.
By ruling in favour of the state, the conservative-majority court effectively ended the constitutional right to an abortion.
Five justices were firmly in favour: Samuel Alito, Clarence Thomas, Neil Gorsuch, Brett Kavanaugh and Amy Coney Barrett.
Chief Justice John Roberts wrote a separate opinion saying that, whilst he supported the Mississippi ban, he would not have gone further.
The three justices who disagreed with the majority – Stephen Breyer, Sonia Sotomayor and Elena Kagan – wrote that they had done so “with sorrow – for this court, but more, for the many millions of American women who have today lost a fundamental constitutional protection”.