The Danish European Sperm Bank has acknowledged the donor’s sperm was overused and immediately blocked him once the mutation was discovered.
A sperm donor who unknowingly carried a rare, cancer-causing mutation has fathered nearly 200 children across Europe, according to a major investigation led by the European Broadcasting Union (EBU), including 14 public service broadcasters.
The man appeared healthy, passed all routine screening, and donated sperm for around 17 years while he was a student. But up to 20 per cent of his sperm carried a mutation in the TP53 gene – a gene that normally prevents cells from becoming cancerous.
Children who inherit the mutation develop Li Fraumeni syndrome, a disorder that gives them up to a 90 per cent chance of developing cancer over the course of their lives.
Some donor-conceived children have already died. Many more are expected to develop cancer throughout their lifetimes.
Doctors first raised the alarm this year after identifying 23 children with the variant out of 67 known cases at the time. Ten had already been diagnosed with cancer.
The investigation found that the donor's sperm was used to conceive at least 197 children across 14 countries – though the true number may be even higher.
Denmark’s European Sperm Bank (ESB), which supplied the samples, reportedly admitted the sperm was used too many times and sent its “deepest sympathy” to affected families.
The bank said the mutation could not have been picked up in screening and that it "immediately blocked" the donor when the issue emerged.
The investigation found that children have been born using the donor's sperm in Denmark, Belgium, Spain, Greece, and Germany.
The sperm was also sold to Ireland, Poland, Albania and Kosovo, and women from Sweden also received fertility treatment from this donor.
Meanwhile a "very small number" of women from the United Kingdom were also treated at clinics in Denmark, according to Peter Thompson, chief executive of the UK's Human Fertilisation and Embryology Authority (HFEA).
Euronews Health has contacted the European Sperm Bank for comment and has not yet received a response.
An extraordinary coincidence and a regulatory failure
Experts say the case exposes cracks in international donor regulation.
"Screening for something de-novo in testis will never work on blood. Each sperm in an ejaculate is slightly different so screening these is also not simple," Jackson Kirkman-Brown, a professor at the University of Birmingham, said in a statement. "In the end the issue here is around family limits and extended un-monitored use."
Meanwhile, Clare Turnbull of The Institute of Cancer Research in the UK described the situation as extraordinarily improbable.
"This represents a highly unfortunate coincidence of two exceptionally unusual events: that the donor's sperm carry mutations for an extremely rare genetic condition … and that his sperm has been used in the conception of such an extraordinarily large number of children," she said.
She said the evidence suggests the mutation arose in the donor’s testes and spread rapidly among sperm cells – "a demonstration of selfish spermatogonial selection."
Rules across Europe
The rules governing sperm and egg donation vary from one European country to another. The maximum number of children from a single donor ranges from one in Cyprus to 10 in France, Greece, Italy, and Poland, according to a 2025 report from the Nordic National Ethics Councils.
Other countries limit the number of families that can use the same donor to give them the opportunity to have brothers and sisters. For example, the same donor can help 12 families in Denmark and six families in Sweden or Norway.
In addition, donations are kept anonymous in 16 countries, although the donor may be disclosed in some of them if the child has severe health conditions, the report found.
