The concept of “fetal viability” is at the center of the U.S. Supreme Court case that could undercut or even eliminate the constitutional right to abortion. Under the court’s precedents, states can’t impose significant restrictions on abortion access before the point of fetal viability. Defending its attempt to ban abortion starting at 15 weeks of pregnancy, Mississippi is asking the court to discard the fetal viability line and give states broad power to restrict abortion at earlier stages. About 7% of abortions in the U.S. -- or about 36,000 a year, using data for 2019 -- take place in the 15th week or later, meaning they could become outlawed in many states. According to a leaked draft of a majority opinion, published by Politico, the court is poised to overturn precedent and side with Mississippi.
In short, it’s the point at which a fetus is capable of living outside the womb with medical intervention. Exactly when it occurs requires a case-by-case determination. The most premature baby known to have survived was born (in 2020) at 21 weeks, 2 days in 2020, but doctors say fetal viability generally occurs a bit later than that. In the 1992 Planned Parenthood v. Casey case, the Supreme Court said viability tended to be around 23 to 24 weeks but could shift toward an earlier date as medical technology improved.