Oliver Conway

Nearly 200 children have been fathered by a sperm donor with a cancer-causing gene mutation.

But how could it happen?

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Every year, egg and sperm donations help thousands of people with fertility issues start families of their own.

But a Europe-wide investigation has found that one sperm donor, who fathered nearly 200 children, unwittingly passed on a genetic mutation that dramatically increased their risk of cancer.

Celine, not her real name, is a single mother in France whose child was conceived 14 years ago.

She received a call from her fertility clinic in Belgium urging her to get her daughter screened.

She told us of her fears over the possibility her child may develop cancer.

We have translated her words.

Some of the children have already died, and only a minority who inherited the mutation will manage to avoid the disease entirely.

I heard more from our health correspondent, James Gallagher.

So this sperm donor donated back as a student in 2005, and we think that that sperm was used in around 67 fertility clinics across 14 countries.

And the European Sperm Bank said it would have not been possible to detect the mutation this man had by preventatively genetically screening him.

And once they did know that he carried this mutation, it was immediately blocked.

But so many women and families are affected and the sperm was used by so many people.