WASHINGTON, Oct 31 — Abortion has been legal in the United States for nearly 50 years but remains an emotional and bitterly contentious issue and access to the procedure varies from state to state.

The Supreme Court is to hear arguments tomorrow challenging a Texas law that prohibits abortion after six weeks, before many women even know they are pregnant.

Here is a synopsis of the state of affairs:

Roe v. Wade

The US Supreme Court ruled in its landmark 1973 decision in Roe v. Wade that access to abortion is a woman’s constitutional right, striking down state laws that restricted the procedure.

In a 1992 ruling in the case of Planned Parenthood v. Casey, the court guaranteed a woman’s right to an abortion until the fetus is viable outside the womb, which is typically around 22 to 24 weeks.

That is longer than in many other countries, where the cutoff is the end of the first trimester, or around 12 weeks.

Individual states retained the right to enact laws protecting a woman’s health so long as they did not impose an "undue burden” on access to abortion of a non-viable fetus.

Patchwork

With "undue burden” being subject to interpretation, a number of conservative US states have imposed a patchwork of restrictions on abortion, forcing many facilities to close their doors.

West Virginia and Mississippi, for example, each have only one abortion clinic while in California there are more than 150.

Among the restrictions are parental consent for minors to undergo an abortion, a 24-hour waiting period, and a requirement to listen to the beating heart of an embryo.

Money is another factor. Some 10 states prohibit private insurance companies from reimbursing for abortions while 15 allow public funds to be used to pay for the procedure for women who cannot afford it.

Poverty and minorities

There were more than 862,000 abortions in the United States in 2017, according to the Guttmacher Institute, an organisation which supports access to contraception and abortion.

That number corresponds to 13.5 abortions for every 1,000 women of procreation age, about the same rate as in other developed countries.

Nearly 50 per cent of the women seeking abortions live below the poverty line and Black and Hispanic women are overrepresented compared with their proportion of the population (29 per cent and 25 per cent respectively).

According to the Centers for Disease Control and Prevention, 92.2 per cent of abortions carried out in the United States take place in the first trimester.

Public opinion divided

Nearly 60 per cent of Americans believe abortion should be legal in all or most cases, a number which has remained relatively stable in recent years, according to a Pew Research Center survey conducted this spring.

But there are enormous differences between Republicans and Democrats on the issue.

Eighty per cent of Democrats and Democratic-leaning independents say abortion should be legal in all or most cases but just 35 per cent of Republicans feel this way, according to the Pew survey.

And the partisan split is getting wider: the numbers were 72 per cent and 39 per cent in 2016.

Religious convictions also play a large role: 77 per cent of white evangelicals believe abortion should be illegal in all or most cases.

A conservative offensive

During the 2016 presidential campaign, Republican Donald Trump attracted votes from the religious right with a promise to name conservative justices to the Supreme Court who share their values and would be inclined to overturn Roe v. Wade.

Trump ended up making three nominations to the Supreme Court, cementing a 6-3 majority on the nation’s highest court.

Their arrival prompted Republican legislators in Texas and other conservative states to pass laws they hoped would force the court to revisit Roe v. Wade.

The strategy has borne fruit with the court examining the Texas law on Monday and a Mississippi law on December 1 that would ban abortion after 15 weeks of pregnancy. — AFP