text: A British mother is among nearly 100 women who have had babies by a Danish sperm donor who has triggered an international scare over the spread of an incurable genetic disease. The man, known only as Donor 7042, carries a defective gene known as neurofibromatosis 1 (NF1) that can pass on a severe, life-limiting condition to his offspring. With demand for Danish sperm soaring, the donor is understood to have fathered 99 ‘Viking babies’ – as they are widely dubbed – across the world through the clinic Nordic Cryobank. Scroll down for video . Ten of his offspring have already been diagnosed with NF1 – a condition which can increase the risk of cancer, cause learning difficulties and reduce a sufferer’s lifespan by up to 15 years. A child born from a parent with the defective gene has up to a 50 per cent chance of developing the disease. Now four families are suing the sperm bank and the case has raised questions among fertility experts about Denmark’s booming, and unregulated, sperm export trade. Laura Witjens, from the National Gamete Donation Trust (NGDT), said: ‘The distribution and use of Danish and American sperm donors is not regulated or monitored, but patients are not told this. ‘NF1 is a rare disease, but the terrible spread of the gene via this prolific Danish donor highlights the worrying dangers of the widespread use of a single donor.’ The British mother was one of 20 women treated at an IVF clinic in Belgium who conceived using the rogue sperm, the Belgian federal health authority revealed. But reports from a variety of countries show the donor has fathered many more children – 99 in total, including the ones on Belgium, along with 44 across Scandinavia, 34 in America and one in Iceland. Danish mother Lone Sogaard-Kristensen, whose daughter inherited Donor 7042’s illness, claims she was contacted by as many as 17 women with his children who had the condition. Ms Witjens said last night that it was possible more British women could have bought his donations with the defective gene online. Donor 7042’s sperm was also exported to a closely associated centre in America – the California Cryobank. But in 2009 it was discovered he carried the NF1 gene – despite undergoing tests and stating in a questionnaire for Nordic Cryobank that there were no genetic disorders in his family. The shock discovery was made when a baby conceived with his sperm in Belgium was diagnosed with the condition. Ms Sogaard-Kristensen was ‘stunned’ to be informed of his medical status by the Danish health authorities. And when her daughter Andrea subsequently developed the illness, she became one of the families – three from Denmark and one from the US – who are taking legal action against Nordic Cryobank. The donor has fathered many more children – 99 in total, including the ones on Belgium, along with 44 across Scandinavia, 34 in America and one in Iceland. A class action lawsuit claims it failed to properly screen for the disorder before using his specimens. ‘The case is not about money or revenge, it is about the fact we have not been able to get any information and the only way we can do this is through a court,’ Ms Sogaard-Kristensen said. ‘There are no rules that say you must be told how many children these donors make and the sperm banks will not tell you.’ A limit should be set on the number of children who can be fathered by sperm donors, to combat fears that siblings or cousins could unwittingly meet and start families, experts say. Clinics are currently allowed to sell sperm from a donor to thousands of women around the world, raising fears of an ‘incest timebomb’. One man could theoretically ‘sire’ an ‘unlimited number’ of children, say the researchers, writing in the journal Reproductive BioMedicine. The panel suggests no donor should sire more than 100 offspring. The case comes as leading fertility scientists from Birmingham University and the Netherlands are calling for new international rules limiting the number of children one donor can produce to 100. They say if a donor exceeds this there is a risk of siblings inter-breeding and suffering psychological damage on finding out they are related to hundreds of other children. Dr Jackson Kirkman-Brown, the fertility expert who led the research at Birmingham University, said: ‘What is clear when buying sperm from abroad is that although the number of families a donor is allowed to father in the UK is capped, it could be hundreds elsewhere. ‘If you can imagine finding out that you have 500 siblings across the globe — that could have a real risk to the mental health of a child.’ It is understood that The Nordic Cryobank will claim that the legal claims against them are unfounded. Managing director Peter Bower has previously stated that Donor 7042 could not be ‘clinically classified as having NF1, as it only occurs in some of his cells’. The company’s website states that it carries out genetic testing for a range of diseases including cystic fibrosis and sickle cell anaemia. But it adds the disclaimer: ‘It is impossible to rule out genetic disease with 100 per cent certainty since it is not possible to test for all inheritable diseases.’
target: Donor 7042 carries defective gene known as neurofibromatosis 1 (NF1)
  Ten of the donor's offspring have already been diagnosed with NF1 .
  Can increase risk of cancer, cause learning difficulties and reduce lifespan .
  Four families are suing the Nordic Cryobank that supplied the sperm .