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 . ’
Donor 7042 carries defective gene known as 2009 ( 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 .