Jérôme Lejeune: A Geneticist In Defense of Life

Servant of God, Pediatrician, Geneticist

Jérôme Lejeune was a French pediatrician and one of the leading geneticists in the world. In 1959, he discovered that the presence of an extra twenty-first chromosome in certain people, which causes Down Syndrome. He then went on to identify other chromosomal disorders and did pioneering research on chromosomal anomalies in cancer.

Jérôme was a strong advocate for the protection of all life from conception to natural death. He spoke out strongly against pre-natal diagnoses that look for chromosomal abnormalities, which often lead to abortion. He was passionately concerned about the welfare of mentally handicapped children. Jérôme died in Paris, France, on Easter Sunday 1994.

Jérôme Lejeune: Led by Wonder

In a message about his friend, Jérôme, St. John Paul II said:

“Professor Jérôme Lejeune was always able to employ his profound knowledge of life and of its secrets for the true good of man and of humanity, and only for that purpose.”

Jérôme sought to comprehend the mystery of life, but also to express it. He communicated a scientific basis for the beginning of life at conception, and sought to understand the causes of Down Syndrome. Jérôme defended the dignity and rights of people living with Down Syndrome, and often testified at court trials when nascent human life was at stake. He would often ask:

“Is life a fact of a desire?”

Jérôme always had a strong sense of wonder. He told his children: “admiring a sunset, contemplating beauty, being aware of the Infinite, and hence being able to reason about the human condition – only man has that grace”.

Wonder and curiosity constantly reinforced each other and led to knowledge. “Understanding the human body, its subtle mechanisms, the origin of life – for him it was an object of study, but also of unending wonder,” his daughter said. “What a marvelously ingenious and complex machine is this body that makes us live!”

Jérôme Lejeune’s Core Motivational Drive

Led by his wonder, Jérôme undertook a career in genetics where he sought a cause for the abnormality of Down Syndrome. At the time, it was often called “mongrolism”. Yet we know it today as Trisomy 21, thanks to Jérôme’s work.

Jérôme wanted to understand the causes for Down Syndrome so that he could communicate the truth. At the time of his work, there were many false ideas about the disease. For instance, many people believed that the mother gave it to her child. Others believed that it was contagious. It was common to see people cross to the other side of the street when they saw a child with Down Syndrome.

Jérôme’s ability to express his finding of an extra chromosome in the 21st pair led to a widespread shift in treatment and perception. He dedicated much of his life to providing compassionate, humane care for all of those born with chromosomal abnormalities. One of his favorite lines was:

“A man is a man is a man.”

Stories of Achievement

Two stories from Jérôme’s life illustrate his core motivational drive to comprehend and express. He was never content simply with exploration and knowledge alone; it was in finding pithy, memorable, and often eloquent ways of expressing the findings of his work that he was able to make such an impression on the world.

The Story of Tom Thumb

Jérôme Lejeune wrote a text in 1973 that summed up forcefully all of the conviction, scientific certitude, and rhetorical talent that made him such an extraordinary defender of life. He explained the evolution of life from the first moment of conception. From the time that an egg is fertilized, it contains all of the genetic material that makes one a member of the human species.

In the text, Jérôme told the story of Tom Thumb, “this little man that we all once were in our mother’s womb”. He illustrated the continuity of life, distilling complex genetic and philosophical concepts to words that are easily grasped by his listeners.

The Testimony about Frozen Embyros

Jérôme testified at a divorce trial in Maryville, TN, in which frozen embryos were at stake. The trial was front page news, which gave Jérôme an opportunity to express his research to millions around the country. He describes the satisfaction of the experience:

“It was a question of explaining, as a genetitist, that it is well known that sufficient information – all that is necessary – was there at the moment of conception, and that there was no doubt that these were very young human beings. Extremely young. Incredibly young. But they were living beings, and their biological inheritance allowed us to declare that they were human. And a being that is human is a human being.”

He continued to explain:

“In order to make the judge understand what was at stake, I used a very simple word. I told him, ‘These very young human being are frozen, packed together by the thousands into an extremely restricted space, where time itself is stopped.”

Jérôme had a deep desire to express his convictions, and his desire to speak out caused him much suffering. He had an insatiable, irresistible, enduring drive throughout his life to speak the truth. In a speech before bellow physicians, he called a United Nations body as an “Institute of health that has become an institute of death.” His defense of life was such an unpopular position in the medical community that he wrote to his wife later that day: “This afternoon I lost my Nobel Prize.”

Summary of a Heroic Life

There is evidence in Jérôme’s life of a pattern of seeking knowledge and understanding for the good of humanity. His daughter recounts an experience near the end of his life:

“Some time before his death, at the hospital, he wanted to see a program devoted to the mission in orbit to repair the Hubble satellite. The human ingenuity thrilled him. It was a mission with only one goal: knowledge. Knowledge was the true human genius for Jérôme.” – Clara Lejeune-Gaymard[1]

Jérôme Lejeune’s mission was to comprehend the mystery of the human body and human life. He found deep satisfaction in communicating that mystery to others. Throughout his life, Jérôme followed his thirst to comprehend. Yet he also found great joy in communicating truth. Because he found such joy in expression, Jérôme’s work will live on. And so will thousands of lives in the womb and beyond.

[1] From the book “Life is a Blessing: A biography of Jérôme Lejeune”


Luke is co-creator of ActivPrayer and Executive Director of Inscape, an organization that he co-founded with Dr. Joshua Miller. Visit his Speaker page here.

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