The US Supreme Court issued a landmark ruling Friday overturning Roe v. Wade and allowing states to ban abortion.

Dobbs v. Jackson Women's Health Organization addresses a 2018 Mississippi law banning abortion after 15 weeks, much earlier than the timeline established by Roe and later cases.

"Roe was egregiously wrong from the start," Justice Samuel Alito wrote in the majority opinion. "Its reasoning was exceptionally weak, and the decision has had damaging consequences."

What exactly did the Supreme Court say in Roe v. Wade? What does the new ruling mean? Here's what you need to know.

What is Dobbs v. Jackson?

In March 2018, the Mississippi Legislature passed HB 1510, the Gestational Age Act, which banned abortion after the first 15 weeks. There are exceptions for a medical emergency or "severe fetal abnormality," but not for cases of rape or incest. Republican Gov. Phil Byrant signed the bill on March 19, 2018.

Jackson Women's Health Organization quickly challenged the law, and in November 2018 the US District Court for the Southern District of Mississippi ruled in the clinic's favor. In December 2019, the Fifth Circuit unanimously upheld the lower court's decision.

Mississippi appealed the ruling to the Supreme Court in October 2021 and justices heard oral arguments in Dobbs v. Jackson Women's Health Organization in December.

How did the Supreme Court rule in Dobbs?

The high court effectively struck down Roe, which protects a woman's right to an abortion in the first 24 weeks. The new ruling reverts regulation to the states, 26 of which have statutes banning or severely restricting abortion. 

"It is time to heed the Constitution and return the issue of abortion to the people's elected representatives," Justice Samuel Alito delivered in the opinion for the court, which was joined by Justices Clarence Thomas, Neil Gorsuch, Brett Kavanaugh and Amy Coney Barrett.

Chief Justice John Roberts delivered a concurring opinion while the court's three liberal justices -- Stephen Breyer, Sonia Sotomayor, Elena Kagan -- dissented.

What is Roe v. Wade?

Roe v. Wade is the 1973 Supreme Court decision that determined that a woman has a constitutional right to an abortion.

In 1969, attorneys for a pregnant Dallas woman filed suit with the US District Court for the Northern District of Texas challenging the state law banning abortion except when the mother's life was at risk.

The court agreed, but Texas appealed directly to the Supreme Court.

Read More: When Will the Supreme Court Rule on Abortion?

In the opinion for the 7-2 majority, Associate Justice Harry Blackmun wrote that denying a woman the right to choose whether to be pregnant violated the due process clause of the 14th Amendment, which, he wrote, protects "the right to privacy, including a woman's qualified right to terminate her pregnancy." 

The decision to have an abortion during the first trimester was between a woman and her doctor, Blackmun wrote. After that, the state may "regulate, and even proscribe, abortion except where necessary … for the preservation of the life or health of the mother."

Who were Roe and Wade?

"Jane Roe" was the pseudonym used by plaintiff Norma McCorvey, who revealed her identity four days after the verdict was announced. 

Henry Wade was the district attorney in Dallas County, Texas, tasked with enforcing Texas' abortion law. 

McCorvey, 22, was a single, unemployed mother of three living in Dallas when she sought to terminate her pregnancy in 1969.

Though she won her case, McCorvey never had the abortion: By the time the Supreme Court rendered its opinion four years later, she had given birth to a girl, whom she put up for adoption.

Was abortion illegal in the US before 1973?

Prior to the 1850s, most US states applied British common law, which permitted abortion before "quickening," when a pregnant woman can first feel the movements of the fetus, at about 15 to 20 weeks.

By 1900, however, most states had classified abortion as a felony except in limited circumstances -- typically if the mother's life was at stake or in the case of rape or incest. 

In 1973, when Roe was argued, only four states -- Alaska, Hawaii, New York and Washington -- had repealed their abortion bans completely. Another 13 had loosened restrictions, according to Planned Parenthood. The decision in Roe v. Wade effectively overturned abortion bans in 30 states.

What other Supreme Court cases have shaped US abortion policy?

Roe v. Wade wasn't the only case impacting a woman's right to choose. A handful of cases before and since have helped establish the current landscape. 

United States v. Vuitch, 1971
Two years prior to Roe, the Supreme Court ruled that a DC law banning abortion was not "unconstitutionally vague" when it made an exception for the health of the mother.

Though Vuitch upheld the district's ban, it established the Supreme Court had jurisdiction to rule on state abortion regulations. 

Planned Parenthood v. Danforth, 1976
Following Roe, the Supreme Court issued several opinions underscoring a woman's right to choose to end a pregnancy. In this ruling, the justices struck down a Missouri statute requiring a married woman to obtain her husband's consent before getting an abortion. 

Harris v. McRae, 1980
The Supreme Court upheld the Hyde Amendment, a congressional measure prohibiting the use of federal funds, namely Medicaid, to pay for an abortion. 

In the majority opinion, Associate Justice Potter Stewart wrote that "it does not follow that a woman's freedom of choice carries with it a constitutional entitlement to the financial resources to avail herself of the full range of protected choices."

City of Akron v. Akron Center for Reproductive Health, 1983
This was one of several cases in the 1980s that rejected informed-consent provisions requiring patients be given information on the medical risks and alternatives to abortion and be subject to a 24-hour waiting period. 

Planned Parenthood of Southeastern Pennsylvania v. Casey, 1992
In this divisive ruling, the court determined state laws could not impose an "undue burden" on a woman's right to have an abortion, a less rigorous standard than the one established by Roe v. Wade. And the responsibility for proving a regulation is extreme falls on the woman, not the government.

Casey involved a challenge to a broad Pennsylvania law that included a 24-hour waiting period and an informed-consent provision -- as well as requirements that a minor obtain permission from at least one parent before obtaining an abortion and for a wife to notify her husband.

All of the provisions of Pennsylvania's abortion law, with the exception of spousal notification, were upheld. 

"The result," wrote the Pew Research Center, "was that a state's interest in and regulation of potential life could now arguably extend throughout a woman's pregnancy." 

The information contained in this article is for educational and informational purposes only and is not intended as health or medical advice. Always consult a physician or other qualified health provider regarding any questions you may have about a medical condition or health objectives.