What Science Says About Abortion

Overturning Roe won’t stop states from tying abortion access to fetal viability

- By David H. Freedman

THE ESSENCE OF THE SUPREME Court’s 1973 Roe v. Wade decision, which established a woman’s right to an abortion, was to balance a pregnant woman’s constitutional right to privacy with the hypothetical rights of a fetus that at some point might be considered a person, even while inside the womb. The Court’s compromise was to confer those hypothetical rights on a fetus when it reaches the 28th week of pregnancy.

That threshold wasn’t arbitrary; it was based on the state of medical science at the time. In 1973, doctors and midwives were sometimes delivering babies prematurely at 28 weeks—but no earlier. Clinical experience established when a fetus could be considered just developed enough to live outside the womb.

In the half-century since, the science of fetal development and early birth has advanced considerably. Neonatal physicians and researchers have modified their thinking on when a fetus is and isn’t viable outside the womb, on how it makes the transition from a bundle of cells to a thinking, feeling being, on the relationship between a fetus and the health of the mother and on the many factors that determine whether a particular premature birth will be successful.

Throughout history, societies have struggled to define human life and to balance the competing interests of mother and child. Aristotle’s notion of “quickening,” when a pregnant woman can first feel movement in her womb, served to differentiate embryo and fetus in early Western laws. The Old Testament refers to “formation,” the point at which a fetus takes on human shape. When safe methods of imaging the womb, such as ultrasound, revealed in the 1950s that movement begins earlier than previously thought, the idea of viability outside the womb emerged as an important legal milestone.