A sweeping cross-border investigation has uncovered how a sperm donor carrying a dangerous, undetected genetic mutation fathered at least 197 children across Europe—leaving families confronting a lifetime of heightened cancer risk and, in some cases, the deaths of their children.
The joint investigation, conducted by 14 public service broadcasters including the BBC through the European Broadcasting Union’s Investigative Journalism Network, reveals that up to 20% of the donors’ sperm carried a mutation in the TP53 gene—central to preventing cells from becoming cancerous. Any child conceived with mutated sperm inherits the variant in every cell of their body, resulting in Li-Fraumeni syndrome, a condition linked to up to a 90% lifetime cancer risk.
Some children have already developed multiple cancers. Some have died.
A Student Donor, 17 Years of Use, No Detection
The donor—anonymous under European guidelines—began selling sperm to Denmark’s European Sperm Bank as a student in 2005. He was healthy, passed standard screening, and is not ill today. But investigators found that a spontaneous DNA mutation had occurred before he was born, affecting a subset of his cells, including up to one-fifth of his sperm.
For 17 years, clinics in 14 countries used his samples, ultimately creating at least 197 children. That number is expected to rise as data from more countries emerge.
Although the sperm was not sold directly to the UK, the Danish authorities notified the UK’s Human Fertilisation and Embryology Authority (HFEA) this week that a “very small number” of British women travelled to Denmark for fertility treatment using this donor’s samples. Those families have been contacted.
“A Dreadful Diagnosis”
Experts say that Li-Fraumeni syndrome is among the most devastating inherited cancer syndromes known.
“It is a dreadful diagnosis… There is a lifelong burden,” said Prof Clare Turnbull, cancer geneticist at the Institute of Cancer Research in London. Children with the syndrome require annual body and brain MRI scans and abdominal ultrasounds; many women pre-emptively remove their breasts due to their high cancer risk.
The European Sperm Bank expressed “deepest sympathy” for affected families and admitted the donor’s sperm “was used to make too many babies” in some countries. It said the mutation could not have been detected through routine screening and that the donor was “immediately blocked” after the problem emerged.
Children Already Diagnosed, Families Already Mourning
Doctors first raised alarms earlier this year when geneticists noticed unusual clusters of children with Li-Fraumeni syndrome linked to sperm donation. Initial counts identified 23 affected children out of 67 known births at the time; 10 had already been diagnosed with cancer.
Further digging by journalists, Freedom of Information requests, and interviews uncovered far higher numbers.
“We have many children who have already developed cancer,” said Dr Edwige Kasper, cancer geneticist at Rouen University Hospital in France, who presented initial findings. “Some children have developed two different cancers and some… have already died at a very early age.”
Families Living Under a Cloud
Céline (not her real name), a single mother in France, learned that her 14-year-old daughter carries the mutation after a Belgian clinic urgently contacted her.
She said she harbours “no hard feelings” toward the donor, but condemned being given sperm that “wasn’t clean, that wasn’t safe, that carried a risk.”
She now lives waiting for the inevitable.
“We don’t know when, we don’t know which one, and we don’t know how many,” she said. “When it happens, we’ll fight. If there are several, we’ll fight several times.”
Used Across 67 Clinics in 14 Countries
The donor’s sperm was sold to:
Denmark, Belgium, Spain, Iceland, Germany, Greece, Cyprus, North Macedonia, Georgia, Hungary, Ireland, Poland, Albania, and Serbia.
Countries enforce their own limits on how many families a single donor can serve, but there is no global law. Belgium allows a donor to be used by six families; instead, 38 women conceived 53 children with this donor’s sperm.
In the UK, the limit is 10 families per donor. Britain now imports roughly half its donor sperm due to shortages, a fact experts say increases vulnerabilities.
“You Can’t Screen for Everything”
Prof Allan Pacey, reproductive expert at the University of Manchester, said international sperm banks make it difficult for countries to contain donor usage.
He described the case as “awful,” but warned that making screening too strict would lead to a complete donor shortage.
“You can’t screen for everything,” he said. “If we make screening even tighter, we wouldn’t have any sperm donors.”
The case follows another controversy involving a donor who fathered over 550 children before authorities intervened.
The European Society of Human Reproduction and Embryology is considering recommending a limit of 50 families per donor, but admits this would not reduce rare genetic risks—only the psychosocial burden of children discovering they have hundreds of half-siblings.
Sperm Banks Defend Screening, But Questions Mount
The European Sperm Bank emphasised that donor sperm remains a lifeline for thousands of families and that cases like this are “vanishingly rare.”
Experts agree that licensed clinics offer the safest option, with screening far beyond what is expected of typical fathers-to-be.
Still, the case raises urgent questions: How many times was the donor used? How many children carry the mutation? And should global usage caps be enforced?
For now, parents who fear they may be affected are urged to contact the clinic where they received treatment and that country’s fertility authority.
The BBC has withheld the donor’s identification number, citing privacy and the fact that families known to be affected have already been alerted.
