Jérôme Lejeune was born on June 13, 1926 at Montrouge in France. Educated in medicine, Jérôme undertook the systematic pediatric genetic research at the Hôpital des Enfants Malades in Paris.
In 1958, Jérôme discovered the chromosomal cause of Down syndrome — the Trisomy 21 (third copy of chromosome 21). The Lejeune discovery established the 20th-century pediatric genetics tradition.
Jérôme undertook the systematic Catholic pro-life engagement — the defense of persons with Down syndrome against the systematic prenatal-screening abortion.
In 1974, Jérôme was appointed to the Pontifical Academy of Sciences by Pope St. Paul VI. In 1994, Pope St. John Paul II appointed Jérôme as the first President of the Pontifical Academy for Life.
Jérôme died at Paris on April 3, 1994 at the age of 67 — shortly after his Pontifical Academy for Life appointment.
Declared Venerable January 21, 2021 by Pope Francis.