A Danish donor whose sperm was used to create at least 197 children across 14 countries in Europe, passed a cancer-causing gene to them, a major investigation has found.

Many of the children developed cancer, with some dying at a very early age.

The donor’s sperm was also sold to Ireland, though records do not show any children having been born from it.

The case highlights the lack of controls over the number of children one donor can procreate, and the danger of using eggs and sperm bought on a commercial market without full knowledge of its genetic heritage.

Sperm from Donor 7069, alias ‘Kjeld’, was made available by the European Sperm Bank (ESB) to 67 clinics between 2006 and 2023, when it was blocked from the market.

‘Kjeld’ was a student in 2005 when he started donating at the Copenhagen branch of the ESB after passing all medical tests.

In 2023, however, a gene mutation which dramatically increases the risk of cancer was discovered in a portion of his sperm cells, after doctors reported seeing children he fathered with the TP53 mutation.

It led to the issuing of an international alert to health authorities and fertility clinics.