The US Supreme Court appears poised to accept a Mississippi law that would bar abortions after 15 weeks of pregnancy, even in cases of rape or incest.
In Wednesday's hearing into the case, conservative justices hinted that a majority backed upholding the law.
A ruling, expected in June, may see millions of women lose abortion access.
Anti-abortion activists are urging the court to "protect unborn children", but experts warn of an increase in maternal mortality if abortion is restricted.
Both sides of the debate regard this case, known as Dobbs v Jackson Women's Health Organization, as an all-or-nothing fight over abortion rights.
Lawyers defending the Mississippi law have asked the court to overturn two previous landmark decisions regarding abortion.
The first, 1973's Roe v Wade, gave women in the US an absolute right to an abortion in the first three months of pregnancy, and limited rights in the second trimester.
In 1992, in Planned Parenthood v Casey, the court ruled that states could not place an "undue burden" on women seeking abortions before a foetus could survive outside the womb, at about 24 weeks.
In the years since, the "foetal viability" standard has acted as a red line in abortion law, preventing any bans on abortion before this time.
But anti-abortion campaigners hope the current ideological makeup of the court has created a new opening. The court, reshaped by three appointments under former President Donald Trump, has been called the most conservative-leaning in modern US history.
What did the court hear?
Addressing the court on Wednesday - with its 6-to-3 conservative majority - Mississippi Solicitor General Scott Stewart told justices that past rulings Roe and Casey "haunt our country" and "poison the law".
He took direct aim at the existing foetal viability standard, arguing it was not "tethered" to the Constitution.
Justice Sonya Sotomayor, a liberal, took issue with this claim, responding: "There's so much that's not in the Constitution".
She warned that the court "would not recover" if Americans saw it as a political body, stepping in to reverse Roe and Casey.
The court would not "survive the stench that this creates in the public perception."
Representing Jackson Women's Health Organization - the only abortion clinic in Mississippi - Julie Rikelman of the Center for Reproductive Rights spoke next, asking the court to strike down the Mississippi law.
"Mississippi's ban on abortion, two months before viability, is flatly unconstitutional under decades of precedent," Rickelman said. Mississippi's law would "force women to remain pregnant and give birth against their will".
US Solicitor General Elizabeth Prelogar also spoke, arguing against the Mississippi abortion ban on behalf of the Biden administration.
"The real world effects of overruling Roe and Casey would be severe and swift," she said, adding that women have come to rely on this "fundamental right".
What are campaigners saying?
If the court strikes down Roe v Wade, or rules that the Mississippi law does not place an undue burden on women seeking abortions, at least 21 states are expected to introduce abortion restrictions, including outright bans after 15 weeks.
In these states, nearly half of US women of reproductive age (18-49) - some 36 million people - could lose abortion access, according to research from Planned Parenthood, a healthcare organisation that provides abortions.
Carol Tobias, president of anti-abortion group National Right to Life, told the BBC she was optimistic the court would step in "to protect unborn children".
"We certainly hope that they will let the Mississippi law stand," she said. "We'd love to see them go even further and say that unborn human beings deserve the same protection as born human beings."
But for other women in Washington DC, the possibility of restricted abortion brought fear.
"I'm not shocked, but I'm scared," said Olivia Dinucci. "Abortion still going to happen, people are going to do it no matter if it's legal or not. However, it will not be safe."
She added: "It's 2021, I cannot believe we have to be fighting this."
And some experts have predicted dangerous ripple effects if abortion is restricted.
"We will see significant increases in maternal mortality, which are already disproportionately experienced by women of colour," said Katherine Franke, director of the centre for gender and sexuality law at Columbia University.
"We will see families descend into greater levels of poverty because the inability to take care of kids, rises in domestic violence."
Who gets abortions in the US?
There were about 630,000 reported abortions in the US in 2019, according to the US Centers for Disease Control. This was an 18 percent decrease compared with 2010.
Women in their 20s account for the majority of abortions - in 2019 about 57 percent were in this age group.
Black Americans get abortions at the highest rate - 27 per 1000 women aged 15-44.
The pro-choice Guttmacher Institute says a lack of access to healthcare plays a role, as does discrimination.
Their 2014 survey found three quarters of people receiving abortions were either on low incomes or below the poverty line in the US.
- BBC