A leaked draft opinion suggests the US Supreme Court could be about to overturn a landmark abortion case.

A decision to overrule the 1973 case of Roe vs Wade would lead to abortion bans in roughly half the states and could have huge ramifications for this year’s congressional elections.

Roe vs 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.

But it remains unclear if the draft represents the court’s final word – opinions often change in the drafting process and big and small ways.

Whatever the outcome, the report published by Politico marks an extremely rare breach of the court’s secretive deliberation process.

“Roe was egregiously wrong from the start,” the draft opinion states.

It was signed by Justice Samuel Alito, a member of the court’s 6-3 conservative majority who was appointed by former President George W Bush.

The document was labelled a “1st Draft” of the “Opinion of the Court” in a case challenging Mississippi’s ban on abortion after 15 weeks, a case known as Dobbs vs Jackson Women’s Health Organisation.

The court is expected to rule on the case before its term ends in late June or early July.

The draft opinion in effect states there is no constitutional right to abortion services and would allow individual states to more heavily regulate or outright ban the procedure.

“We hold that Roe and Casey must be overruled,” it states, referencing the 1992 case Planned Parenthood vs Casey that affirmed Roe’s finding of a constitutional right to abortion services but allowed states to place some constraints on the practice.

“It is time to heed the Constitution and return the issue of abortion to the people’s elected representatives.”

A Supreme Court spokeswoman said the court had no comment on the document, which dates from February.

What would be the ramifications of this judgement? US Correspondent Emma Murphy gives her analysis:

If you want an idea of how ferocious and divisive the debate over abortion is in the United States, the apparent leak of a draft judgement should give fair indication.

The fact that such a highly classified document has become public tears at the heart of the Supreme Court itself.

There is an accepted confidentially in the hallowed legal chambers, an acceptance that what is said becomes public only at the moment the justices deem it to be so.

Who leaked it and how will cause divisive suspicion in an already divided institution.

Why someone would take such a risk speaks to the strength of feeling surrounding abortion in America.

If, as the leak suggests, the Supreme Court has provisionally voted to overturn Roe vs Wade, the legislation that legalised abortion nationwide, it would effectively ban millions of women from seeking an abortion.

Individual states could define their own policies and once again it will be divided down party lines. Blue states mainly allowing, red states often banning.

Within minutes of the leak the barricades started going up around the Supreme Court. It seems they may be needed inside and out. This will be a moment of huge outrage, about the leak itself and its content.

The Supreme Court is described as “distinctly American in concept and function.” It certainly seems to be as distinctly divided as the country itself.

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Politico said only that it received “a copy of the draft opinion from a person familiar with the court’s proceedings in the Mississippi case along with other details supporting the authenticity of the document.”

The draft opinion strongly suggests that when the justices met in private shortly after arguments in the case on 1 December, at least five voted to overrule Roe and Casey, and Alito was assigned the task of writing the court’s majority opinion.

Votes and opinions in a case aren’t final until a decision is announced or posted on the court’s website.

The report comes amid a legislative push to restrict abortion in several Republican-led states – Oklahoma being the most recent – even before the court issues its decision.

Critics of those measures have said low-income women will disproportionately bear the burden of the new restrictions.