You've heard of Roe v. Wade -- and you've probably heard that the U.S. Supreme Court may be about to overturn it.

But what exactly is Roe v. Wade, and why does it matter whether it's overturned?

Here's what to know:

Roe v. Wade was a legal case decided by the Supreme Court of the United States in January 1973.

"Wade" refers to Henry Wade, the district attorney of Dallas County, Texas. "Roe" is the pseudonym of Norma McCorvey, a Louisiana woman who had filed a lawsuit in Texas to get an abortion, which was illegal at the time. Despite her involvement in the case, McCorvey never actually got an abortion. In fact, she eventually converted to Protestant Christianity and later to Catholicism, and engaged in pro-life ministry in her later years.

In their opinion, the justices ruled that states could not ban abortion before viability, which the court determined to be 24 to 28 weeks into pregnancy. The legal reasoning centered on the Due Process Clause of the 14th Amendment, which the court interpreted as conferring a "right to privacy" for women seeking abortions.

The makeup of the court at that time, which issued the ruling by a 7-2 vote, was entirely male -- the first female justice, Sandra Day O'Connor, would not arrive at the court until eight years later.

Nearly 20 years later, the court upheld Roe in the case Planned Parenthood v. Casey. The 1992 ruling said that while states could regulate pre-viability abortions, they could not enforce an "undue burden," defined by the court as "a substantial obstacle in the path of a woman seeking an abortion of a nonviable fetus."

What effects has Roe had since the decision was made?

The immediate effect was the legalization of abortion throughout the entire United States, until roughly the end of the second trimester. Abortion was already legal in some form in several states -- such as Colorado, Hawaii, and New York-- before Roe changed the status quo for the entire country.

Abortion rates in the U.S. rose in the years following Roe, peaking at an estimated 1.4 million per year in 1990. In 2019, the latest year government figures are available, there were an estimated 630,000 abortions.

Since Roe and Casey, every state regulation on abortion that has been proposed or passed has had to be viewed through Roe's legal framework of "strict scrutiny", and later through Casey's "undue burden" standard. Dozens of state regulations have been struck down by courts over the years for being out of step with Roe, and thus unconstitutional.

Is there a chance Roe could be overturned now?

Yes. A case currently before the court, Dobbs v. Jackson Women's Health Organization, involves a 2018 Mississippi law restricting most abortions after 15 weeks. The case centers on the question of "Whether all pre-viability prohibitions on elective abortions are unconstitutional," or whether states can ban abortion before a fetus can survive outside the womb, making it a direct challenge to Roe and Casey.

What will happen if Roe is overturned?

If the Supreme Court overturns Roe v. Wade, the question of abortion legalization or restriction will return to the states. State policy would vary widely on the question of abortion, with the practice being automatically outlawed in several states, and explicity protected in others.

If Roe is overturned and women who would have chosen an abortion are unable to get them, many more babies and mothers will need care than previously. Pro-life organizations are marshalling resources to offer support.

That said, abortions will continue in states which have passed laws to protect access to it, and some states, such as Colorado, have explicitly positioned themselves as destinations where women can travel from states with restrictions to avail themselves of abortions.

The federal government under President Joe Biden has attempted preemptively to pass a bill codifying Roe v. Wade into federal law, which if passed would supersede state-level pro-life laws, but such attempts so far have failed.

What will happen if Roe is not overturned?

There are a number of scenarios that could come to fruition that involve Roe remaining in place.

If the Supreme Court does not overturn Roe, but upholds Mississippi's 15-week ban, other states with a court-blocked 15-week bans, such as Arizona, could see their laws come into effect. Additionally, other pro-life states may pass 15-week bans now that they are constitutionally allowed to do so.

??If the Mississippi law is struck down, and Roe and Casey are affirmed, it would be a devastating setback for the pro-life movement, which has pinned its long-term legal strategy on someday having a "conservative" supermajority on the Supreme Court, as is the case today.

So... How likely is it that Roe v. Wade will be overturned?

A leaked draft opinion of the U.S. Supreme Court, which has been confirmed to be genuine though not necessarily final, suggests that the court is indeed poised to overturn Roe v. Wade.

The draft, reported on May 2 after being leaked to Politico, shows the court siding with Mississippi, as well as a thoroughly repudiating Roe and Casey.

"We hold that Roe and Casey must be overruled," Associate Justice Samuel Alito writes in the 98-page draft document, which is labeled as the "Opinion of the Court."

"It is time to heed the Constitution and return the issue of abortion to the people's elected representatives."

The Politico news report said that four justices had joined Alito in the majority, three are preparing dissents, and Chief Justice John Roberts -- often a swing vote -- had not yet settled on a side.

Whatever the court ultimately decides, the consequences for the country will be enormous.