A sperm donor who unknowingly harbored a genetic mutation that dramatically raises the risk of cancer has fathered at least 197 children across Europe, a major investigation has revealed.
Some children have already died and only a minority who inherit the mutation will escape cancer in their lifetimes.
The sperm was not sold to UK clinics, but the BBC can confirm a 'very small' number of British families, who have been informed, used the donor's sperm while having fertility treatment in Denmark.
Denmark's European Sperm Bank, which sold the sperm, said families affected had their 'deepest sympathy' and admitted the sperm was used to make too many babies in some countries.
The sperm came from an anonymous man who was paid to donate as a student, starting in 2005. His sperm was then used by women for around 17 years.
He is healthy and passed the donor screening checks. However, the DNA in some of his cells mutated before he was born, damaging the TP53 gene, which prevents the body's cells from turning cancerous.
Most of the donor's body does not contain the dangerous form of TP53, but up to 20% of his sperm may. Any children conceived from affected sperm will have the mutation in every cell of their bodies, with an associated risk of up to 90% of developing cancer, including childhood cancers like leukemia.
The investigation was conducted by 14 public service broadcasters, including the BBC, and has exposed serious flaws in donor screening protocols and the impacts of unregulated sperm donation practices.
