The Supreme Court heard arguments Wednesday on a Mississippi law that would ban most abortions after 15 weeks. The case provides a clear path to diminishing Roe v. Wade, the 1973 ruling in which the court determined a constitutional right to abortion.

The court is also expected to rule on whether a new Texas law can remain in effect while its legality is challenged. In September, the justices refused to preemptively block the statute from taking effect, despite Roe. The law, which bans almost all abortions after six weeks, is the most restrictive in the nation.

According to the Guttmacher Institute, an organization focused on reproductive health and rights, if Roe v. Wade were overturned, 21 states would ban or severely restrict abortion access. Of those, nine states have pre-Roe abortion bans on their books that would become enforceable again if the precedent is overturned (Texas’s is permanently enjoined by a court order). And 12 states have passed post-Roe “trigger laws” — bans that would take effect in that case. Fourteen states and the District of Columbia have policies that explicitly protect the right to abortion.

Court orders have halted pre-viability bans in many states

Restrictions on abortion rights have increased in the past decade as policymakers in mostly Republican-led states have sought to provoke a Supreme Court challenge to the 1973 precedent by banning abortion before viability. Until the Texas law, federal judges have cited Roe and other precedents in blocking early-stage abortion bans in other states before they took effect.

Thus far, pre-viability bans from 16 states have been blocked by court orders and have not gone into effect. Twenty-one states have pre-viability bans in effect for pregnancies between 20 and 24 weeks. In reviewing the Mississippi law, which would ban almost all abortions after 15 weeks of pregnancy, the Supreme Court said it would examine whether “all pre-viability prohibitions on elective abortions are unconstitutional.”

Seven states — Alaska, Colorado, New Hampshire, New Jersey, New Mexico, Oregon and Vermont — don’t impose any bans based on gestational periods.

The length of a pregnancy is commonly calculated from the start of a person’s most recent menstrual period. Many people don’t know they’re pregnant until after the sixth week.

An average pregnancy lasts about 40 weeks, and viability, the point at which a fetus could survive outside the uterus, generally falls between 24 and 26 weeks. Federal and state courts had consistently blocked enforcement of laws that ban abortion before 18 weeks, until September.

Mississippi currently bans most abortions after 20 weeks, and 16 other states ban them at 22 weeks from the last menstrual period. These bans violate Supreme Court rulings, but the laws were never challenged and went into effect.

State abortion policies have become more extreme compared with 21 years ago

Since 2000, the Guttmacher Institute has evaluated how hostile or supportive each state is toward abortion. States with more protections are deemed more supportive, and states with more restrictions are considered more hostile. Over time, the country has become more extreme in both directions.

The ratings are based on six key abortion restrictions and six protections for access. A state with all the restrictions and no protections has the highest restriction rating and is considered extremely hostile. Six states have that maximum level. A state with all six protections and no restrictions has the highest protection rating and is considered extremely supportive. Only California meets that threshold.

This growing policy divide between states reflects an increase in abortion-related legislation. More than half of all abortion restrictions in the country have been enacted since 2001, most of them concentrated in the South and Midwest. Only 43 efforts to improve access have been enacted in the past 20 years.

This year has seen more restrictions enacted than in the past three years combined. Momentum around abortion restrictions has been growing in the past decade, culminating with the nomination of Justice Amy Coney Barrett in 2020. Her ascension to the court, replacing liberal Justice Ruth Bader Ginsburg, solidified its conservative majority and emboldened abortion opponents who had been seeking ways to strike down Roe.

“Some states have adopted so many restrictions that just about all that was left was to ban abortion,” said Elizabeth Nash, the principal policy associate for state issues at the Guttmacher Institute.

Nash argues that abortion restrictions exacerbate logistical and financial obstacles for marginalized communities, such as racial minorities, low-income people and people in rural communities, and that further rollbacks of abortion rights will only increase the burdens on these populations.

“Those with more resources and privilege would most likely find ways to get the care they need,” she said. “Abortion is health care, plain and simple.”

Danielle Rindler contributed to this report. Sources: Guttmacher Institute.

correction

A previous version of the "When in a pregnancy states have tried to ban abortions" chart abbreviated Arkansas incorrectly. Arkansas, not Alaska, has passed bans at conception and 12 weeks. A previous version of the text also misspelled Ruth Bader Ginsburg's name.