Sperm from a donor carrying a cancer-causing gene was used to conceive about 200 children.

A sperm donor who unknowingly harbored a genetic mutation that dramatically increases the risk of developing cancer fathered at least 197 children across Europe, a major investigation has revealed.

Some children have already died, and only a few who inherit the mutation will remain cancer-free during their lifetime.

The sperm was not sold to British hospitals, but the BBC was able to identify a “very small” number of British families who had been informed that they had used donor sperm while undergoing infertility treatment in Denmark.

The European Sperm Bank in Denmark, which sold the sperm, said it had its “deepest sympathies” with the families affected and acknowledged the sperm had been used to produce too many babies in some countries.

This survey was conducted by 14 public broadcasters, including the BBC, as part of the Investigative Journalism Network under the European Broadcasting Union.

The sperm came from an anonymous man who had been paid to donate as a student since 2005. His sperm was then used by women for about 17 years.

He is healthy and has passed donor screening. But before he was born, the DNA in some of his cells mutated.

This damaged the TP53 gene, which plays an important role in preventing the body’s cells from turning cancerous.

Although most of the donor’s body does not contain dangerous forms of TP53, up to 20% of sperm do contain dangerous forms of TP53.

However, any child born from affected sperm will have the mutation in every cell of the body.

This is known as Li Fraumeni syndrome and causes up to a 90% chance of developing breast cancer, especially in childhood and later in life.

“This is a terrible diagnosis,” Professor Claire Turnbull, a cancer geneticist at the Institute of Cancer Research in London, told the BBC. “It’s a very difficult diagnosis to have it in your family. There’s the burden of having to live your whole life with that risk. It’s definitely devastating.”

Annual MRI scans of the body and brain and abdominal ultrasound are required to detect tumors. Women often choose breast removal surgery to lower their risk of developing cancer.

The European Sperm Bank said, “The donor himself and his family are not sick,” and “These mutations are not detected as a preventive measure through genetic testing.” They said they ‘immediately cut off’ the donor when they discovered problems with the sperm.

Doctors who treated children with cancer linked to sperm donation raised concerns at the European Society of Human Genetics this year.

They reported finding 23 of the 67 children known at the time to have the variant. Ten people have already been diagnosed with cancer.

Through Freedom of Information requests and interviews with doctors and patients, we can reveal that many more children have been born from donors.

This figure is at least 197 children, but may not be the final number as data was not collected from all countries.

It is also not known how many of these children have inherited the dangerous variant.

“There are a lot of children who already have cancer,” Dr. Edwige Kasper, a cancer geneticist at Rouen University Hospital in France who presented the initial data, told the survey.

“There are children who have already had two different cancers and some of them have already died at a very young age.”

Celine, not her real name, is a single mother in France who became pregnant with donor sperm 14 years ago and gave birth to a child with a mutation.

She received a call from the fertility clinic she used in Belgium urging her to get her daughter tested.

She said she had “absolutely no hard feelings” towards the donor, but said it was unacceptable that she received sperm that was “unclean, unsafe and carries risks.”

And she knows cancer is coming for them for the rest of their lives.

“We don’t know when, which one or how many,” she says.

“I understand that there is a good chance that it will happen, and if it does happen, we will fight, and if there are multiple people, we will fight multiple times.”

Donor sperm was used in 67 fertility clinics in 14 countries.

The sperm was not sold to UK hospitals.

However, as a result of this investigation, Danish authorities notified the British Human Fertilization and Embryology Authority (HFEA) on Tuesday that British women had visited Denmark to receive infertility treatment using donor sperm.

The women were informed.

HFEA chief executive Peter Thompson said: “A very small number of women were affected and they heard about the donor from the Danish hospital where they had been treated.”

It is unknown whether the British woman received treatment in other countries where the donor’s sperm was distributed.

Concerned parents are advised to contact the clinic they used and the maternity authority in their country.

The BBC has decided not to publish the donor’s identification number because the donor gave in good faith and because a known case has been contacted in the UK.

Worldwide, there are no laws governing how many times a donor’s sperm can be used. However, individual countries set their own restrictions.

The European Sperm Bank acknowledged that these restrictions were “unfortunately” breached in some countries and was “in dialogue with Danish and Belgian authorities.”

In Belgium, it is stipulated that only six families can use one sperm donor. Instead, 38 women gave birth to 53 children from donors.

The limit in the UK is 10 families per donor.

Professor Allan Pacey, who ran the Sheffield sperm bank and is now vice-chancellor of the Faculty of Biology and Health at the University of Manchester, said countries had become dependent on large international sperm banks and now half of Britain’s sperm is imported.

He told the BBC: “We have to import it from large international sperm banks who also sell it to other countries. That’s how they make their money and that’s where the problem begins, because there is no international law on how often sperm can be used.”

He called the incident “horrible” for everyone involved but said it would be impossible to make the sperm completely safe.

“You can’t test everything. Current testing methods only accept 1% ​​or 2% of all men who apply to donate sperm. So if you make it more stringent, you end up with no sperm donors. That’s the balance.”

This incident, along with the case of a man who had 550 children through sperm donation and was then ordered to stop, has once again raised questions about whether stricter standards should be applied.

The European Society of Human Reproduction and Embryology recently proposed a limit of 50 families per donor.

However, he said this would not reduce the risk of inheriting rare genetic diseases.

Rather, it would be better for the children’s well-being if they discovered that they were one of hundreds of half-siblings.

Sarah Norcross, director of the Progress Educational Trust, an independent charity for people affected by infertility and genetic disorders, said: “More needs to be done to reduce the number of families born from the same donor globally.”

“We don’t fully understand the social and psychological impact of having hundreds of half-siblings – it could be potentially traumatic,” she told BBC News.

“Especially in light of this incident, it is important to remember that thousands of women and couples have no chance of having a child without the help of donor sperm,” the European Sperm Bank said.

“In general, it is safer to have a child with the help of donor sperm if the sperm donor is screened according to medical guidelines.”

Sarah Norcross said such cases were “almost rare” considering the number of children born to sperm donors.

All the experts we spoke to said using a licensed clinic meant their sperm would be tested for more diseases than most fathers-to-be.

Professor Pacey said he would ask: “Is this a British donor or a donor from somewhere else?”

“If it’s a donor from somewhere else, I think it’s legitimate to ask questions about whether that donor has been used before or how many times this donor will be used.”

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