A Danish man who fathered 43 children at 14 different IVF clinics in ten different countries by donating sperm, passed on a genetic disorder known as NF1 to at least five babies born from IVF procedures, it has been revealed.

The man was allowed to continue donating, despite national rules in Denmark restricting donors to 25 times.

The discovery has prompted Danish national health service to restrict the number of times a single person can donate sperm to 12, the BBC reports.

It is not known how many of the children have developed the nerve disorder Neurofibromatosis type I, a condition that causes non-cancerous tumours to grow around nerves, resulting in scoliosis, learning difficulties, eye problems, and epilepsy.

The clinic, Nordisk Cryobank, admitted that the incident was a result of inadequate testing.

Clinic director general, Peter Bower, told Agence France Press that Denmark’s rules regarding confidentiality prevented him from giving information on the children’s age or nationalities.

A Swedish national news service, however, revealed that at least 18 children in Sweden and Norway have been conceived using sperm from the same man, identified as “donor 7042”.

The clinic has admitted they knew as early as 2009 that at least one of the children born from the man’s sperm had been diagnosed with the disease, but had failed to act.

“Our team of physicians and our geneticist looked at the case but didn’t consider there to be reason enough to suspect it was the donor and therefore no reason to stop the use of his sperm,” Bower said.

A 2010 study by the Commission on Parenthood, a part of the Institute for American Values, a pro marriage US think tank, found that children conceived using donor sperm were more likely than the average to develop long-term problems such as depression, delinquency, and substance abuse.

Titled, “My Daddy’s Name is Donor: A New Study of Young Adults Conceived Through Sperm Donation,” the study found that young people conceived through artificial means are “more confused, and feel more isolated from their families” than children born through natural means.

Two-thirds of those surveyed agreed, ‘My sperm donor is half of who I am.’ About half said they are disturbed that money was involved in their conception. More than half said that when they see someone who resembles them they wonder if they are related.

Nearly half say they have feared being attracted to or having sexual relations with someone to whom they are unknowingly related, the study found.

Further, two thirds said that donor offspring have a right to know about their origins, a right that is so far not upheld by the law.

“About half of donor offspring have concerns about or serious objections to donor conception itself, even when parents tell their children the truth,” the study said.