Clinics have already begun closing in some US states after a Supreme Court ruling removed the constitutional right to abortion.
About half of states are expected to introduce new restrictions or bans after the court overturned its 50-year-old Roe v Wade decision. Of these 13 have outlawed abortion instantly.
President Joe Biden has described the ruling as "a tragic error" and protests are under way in cities across the US.
At an abortion clinic in Little Rock, Arkansas - a state with a so-called trigger law allowing an instant ban - the doors to the patient area shut as soon as the court's opinion was posted online and sobbing could be heard. Staff made calls to tell women that their appointments were cancelled.
"No matter how hard we prepare for bad news, when it finally hits, it hits hard. Having to call these patients and tell them Roe v Wade was overturned is heartbreaking," nurse Ashli Hunt told the BBC.
President Biden who said it will dramatically change life for millions of women in America and is expected to exacerbate growing tensions in a deeply polarised country.
The court, in a 6-3 ruling powered by its conservative majority, upheld a Republican-backed Mississippi law that bans abortion after 15 weeks of pregnancy. The vote was 5-4 to overturn Roe, with conservative Chief Justice John Roberts writing separately to say he would have upheld the Mississippi law without taking the additional step of erasing the Roe precedent altogether.
The reverberations of the ruling will be felt far beyond the court's high-security confines - potentially reshaping the battlefield in November's elections to determine whether Biden's fellow Democrats retain control of Congress and signalling a new openness by the justices to change other long-recognised rights.
The ramifications of the decision have reached Aotearoa with Foreign Affairs Minister Nanaia Mahuta tweeting that it was "draconian" and does not support women's right to choose.
However, the Vatican's Academy for Life praised the decision, saying it challenged the world to reflect on life issues, but also called for social changes to help women keep their children.
The Vatican department also said in a statement that the defence of human life could not be confined to individual rights because life is a matter of "broad social significance".
Archbishop Vincenzo Paglia, who heads the Pontifical Academy for Life, said the court's decision was a "powerful invitation to reflect" on the issue at a time when Western society "is losing passion for life".
"By choosing life, our responsibility for the future of humanity is at stake," Paglia said.
Biden took the opposite view, saying on a broadcast: "Today the Supreme Court of the United States expressly took away a constitutional right from the American people that it had already recognised.
"This is a sad day for the country in my view. But it doesn't mean the fight's over. Let me be very clear and unambiguous: the only way we can secure a woman's right to choose a balance that exists is for Congress to restore the protections of Roe v. Wade as federal law."
He urged voters to elect more senators and representatives who would cement a woman's right to choose into federal law.
"I've warned about how this decision risks the broader right to privacy for everyone ... The right to make the best decisions for your health."
The World Health Organisation's Director General Tedros Adhanom Ghebreysus also condemned the ruling.
"I am very disappointed, because women's rights must be protected. And I would have expected America to protect such rights," he said.
UN Secretary General Antonio Guterres said: "Sexual and reproductive health and rights are the foundation of a life of choice, empowerment and equality for the world's women and girls ... Restricting access to abortion does not prevent people from seeking abortion, it only makes it more deadly."
US House Speaker Nancy Pelsosi described it as outrageous and heart-breaking.
She said that a "Republican-controlled Supreme Court" has achieved that party's "dark and extreme goal of ripping away women's right to make their own reproductive health decisions.
"But make no mistake: the rights of women and all Americans are on the ballot this November."
Planned Parenthood was also critical: "SCOTUS [the Supreme Court] may have just ended our constitutional right to abortion, but know this: Abortion is health care, and you deserve to control your body and your future, no matter what. That hasn't changed. We can't and we won't back down now."
Former US president Barack Obama said the Supreme Court had not only reversed nearly 50 years of precedent, "it relegated the most intensely personal decision someone can make to the whims of politicians and ideologues - attacking the essential freedoms of millions of Americans".
Other world leaders joined in the criticism with French President Emmanuel Macron saying abortion was a fundamental right for all women.
"We must protect it. I would like to express my solidarity with all those women whose freedoms have today been compromised by the US Supreme Court."
Canadian Prime Minister said the decision was "horrific".
"My heart goes out to the millions of American women who are now set to lose their legal right to an abortion ... No government, politician, or man should tell a woman what she can and cannot do with her body."
And UK Prime Minister Boris Johnson said: "I think it's a big step backwards ... I've always believed in a woman's right to choose and I stick to that view and that is why the UK has the laws that it does."
Decision hailed by Republicans
Prominent Republicans have welcomed the ruling with former president Donald Trump saying: "This is following the Constitution, and giving rights back when they should have been given long ago ... This brings everything back to the states where it has always belonged."
Though Trump is no longer in office, the overturning of Roe v Wade will be heralded by many supporters as the capstone of his legacy.
While serving as president, he nominated three Supreme Court justices to the bench - tipping the court's ideological balance to a 6-3 conservative majority.
Today, all of the justices nominated by Trump - Neil Gorsuch, Brett Kavanaugh and Amy Coney Barrett - voted to overturn Roe and uphold Mississippi's abortion ban.
And his former deputy Mike Pence said: "Today, Life Won. By overturning Roe v. Wade, the Supreme Court of the United States has given the American people a new beginning for life, and I commend the justices in the majority for having the courage of their convictions."
Senate Republican leader Mitch McConnell described the decision as an historic victory for the Constitution and for the most vulnerable members of US society.
- Reuters / BBC