In the early 1960s, Dr. Frances Oldham Kelsey of the U.S. Food and Drug Administration became one of the most celebrated women in America when she prevented a deadly sedative from entering the U.S. market. A Canadian-born pharmacologist and physician, Kelsey saved countless Americans from the devastating side effects of thalidomide, routinely given to pregnant women to prevent morning sickness.

As the FDA medical officer charged with reviewing Merrell Pharmaceutical’s application for approval in 1960–1961, Kelsey was unconvinced that there was sufficient evidence of the drug’s efficacy and safety. Despite substantial pressure, she held her ground for nineteen months while the extent of the drug’s worldwide damage became known—thousands of stillborn babies, as well as at least 10,000 children across forty-six countries born with severe deformities such as missing limbs, arms, and legs that resembled flippers, and improperly developed eyes, ears, and other organs.

As a result of Kelsey’s efforts, thalidomide was never sold in the United States. The incident led Congress to pass the 1962 Drug Amendment, which fundamentally changed drug regulation in America. Those regulations, still in force today, required pharmaceutical companies to conduct phased clinical trials, obtain informed consent from participants in drug testing, and warn the FDA of adverse effects, and it granted the FDA important controls over prescription-drug advertising.

One of a small minority of women to earn an advanced degree in science in the 1930s, Kelsey faced challenges that resonate with women scientists to this day. Revered by the public as a “good mother of science,” she went on to act as a formidable gatekeeper against other suspect drugs, such as diesthylstilbestrol (DES) and laetrile. As part of the team that tested anti-malarial drugs on prisoner volunteers during World War II, she later was instrumental in the formulation of ethical protocols for drug testing on prisoners and the vulnerable, including the elderly and children.

Yet behind the public adulation, she faced professional jealousies and glass ceilings, political interference with FDA’s actions, and ongoing hostility from pharmaceutical industry officials. She was sustained and supported by family and friends, co-workers and mentors, and a lifetime commitment to good science.

Based upon FDA archival records, private family papers, and interviews with family and colleagues, this biography highlights the efforts and legacy of a pioneering woman of science whose contributions are still influential today.