Abortion Laws Treat Viability as a Bright Line. It Isn’t.

In 2021, Kate Dineen was standing in her kitchen in Boston when her doctor told her over Zoom that her son had experienced a catastrophic stroke in utero. There was only a 50 percent chance the baby would survive after birth, with zero chance of a healthy outcome. Dineen was devastated; she’d previously had a miscarriage and anxiously tracked pregnancy milestones. Still, the decision about what to do next was clear to her and her husband, she told me: “We felt motivated to protect our son from what would have been a life of suffering, however brief.”

But Dineen was 33 weeks pregnant, and when she asked her doctor about her options, she learned Massachusetts banned abortion after 24 weeks. That cutoff roughly corresponds with the “viability line,” or the point in pregnancy when the fetus has a good chance of surviving outside the uterus. There were exceptions if her own health was in danger, and for “lethal” fetal diagnoses, but the stroke didn’t qualify. Once the fetus reached “viability,” Dineen says, she became “an incubator in the eyes of the state.”

For decades, abortion opponents have slung around sensational terms like “late term” and “partial birth” in their efforts to block abortion outright. On its face, banning the procedure after fetal viability might appear like the moderate position—after all, people of all political stripes express discomfort with later abortions, and abortions after 20 weeks’ gestation are extremely rare. But viability is an imprecise term, more ambiguous than meets the eye, and one state recently opted to ditch it altogether.

Today, anything with the promise to live or succeed can be described as viable: a seed, a business plan, a political candidate. But the word originated as a descriptor for a baby. “Viable” entered the English lexicon in the 1820s, when Dr. Theodric Beck borrowed the term from French to describe the moment a fetus was “capable of living” and could therefore inherit a dead parent’s estate. Another doctor, R.E. Griffith, expanded on the idea in an essay titled “Remarks on Feticide,” arguing that in order to convict the mother of a dead newborn, courts must first establish that her child was “viable” at birth. To prove this, Griffith considered various techniques, including an old method of cutting out the lungs and placing them in water—reasoning that if they floated, the baby had likely drawn breath and was not just “a mere parasite of the mother.”

Even as medicine evolved in the ensuing 150 years, doctors’ use of viability as a metric of personhood held fast. Then, in Roe v. Wade, the Supreme Court seized on the concept as a compromise between abortion rights supporters and opponents, declaring a constitutional right to abortion nationwide—but only until fetal viability. States could ban abortion afterward, as long as they allowed exceptions to save the mother’s life.

What determines viability, though? There was always something fraught about the court drawing a line at a stage that is, by nature, more a calculation of probability than a guarantee of survival. According to the American College of Obstetricians and Gynecologists, the leading US professional association for OB-GYNs, fetal viability is based on internal and environmental factors: gestational age, sex, genetics, weight, the availability of neonatal care, and circumstances around delivery. “Even with all available factors considered, it still isn’t possible to definitively predict survival,” ACOG warns. Generally, viability is considered to be 23 to 25 weeks today—down from about 28 weeks in 1973—though babies born so early have only about a 50 percent chance of survival and often suffer long-lasting complications. Artificial uteruses could someday lead to even younger preemies.

Supreme Court Justice Samuel Alito zeroed in on these ambiguities when he voted to overturn Roe in 2022. “Is a fetus viable with a 10 percent chance of survival? 25 percent? 50 percent? Can such a judgment be made by a State?” he wrote, handing states the power to outlaw abortion at any point they wanted.

With more than a dozen states enacting near-total bans, factions of the pro-choice movement embraced viability in their efforts to safeguard dwindling rights. In the years since Roe was overturned, voters in four states have enshrined a right to abortion until viability into their state constitutions, with limited exceptions afterward—language designed to cover most patients while securing support from voters uneasy about abortion later in pregnancy. (In November, voters in Nevada and Virginia passed similar compromise initiatives.)

But other advocates argue that viability bans still allow the government to interfere in a decision that should remain between a patient and her doctor. In her 2025 memoir, Beyond Limits, Dr. Shelley Sella, the first female physician in the US to openly provide third-trimester abortions, says that by the time women came to her, they’d considered “all the factors relevant to their wellbeing and to their unborn child’s.” Her patients included domestic abuse survivors, women whose birth control failed, and, increasingly before she retired, those who sought abortions earlier in pregnancy but were prevented by state laws from obtaining them. “You don’t know the story until you are the story,” she remembers a patient telling her.

Dineen ultimately was able to terminate her pregnancy by traveling to Maryland, one of nine states where third-trimester abortions were legal. When she returned home, she started working with reproductive rights advocates to change the law in Massachusetts. First, in 2022, they broadened their state’s exception to include “grave” fetal diagnoses, but patients were still falling through the cracks. So this past summer, the legislature passed a new law eliminating the viability line entirely. Massachusetts now leaves the question of later abortions to the “professional judgment of the physician.”

“Pregnancy is complex, and there’s too much gray area to be governed by laws that are black and white,” says Dineen, now a mother of two. “It’s not about a specific fetal diagnosis, it’s not about the specific number of weeks, but it’s really about who gets to decide: Is it the patient and their doctor, or is it the letter of the law, the government?”