By Michelle Roberts
Health reporter, BBC News
Donor sperm is screened for infections
Experts are questioning how rigorously sperm donors must be screened after nine children have inherited a heart condition from their biological father.
The 23-year-old man was unaware of his heritable condition, a cardiomyopathy, that has killed one of the children.
Donors are asked if diseases run in the family, but some are not obvious.
US doctors are saying in the Journal of the American Medical Association that cardiomyopathy should be added to the list routinely checked for in donors.
But UK experts warn this may be a step too far, and that more checks will be a turn off for donors.
At least 1 in 500 people in the UK are thought to have hypertrophic cardiomyopathy.
While the condition itself, which affects the heart muscle, may go unnoticed, a minority of sufferers are at risk of sudden death.
It is a dominant genetic disorder, which means that each child of an affected person has a 50:50 chance of inheriting the condition.
Symptoms can be absent or vague - chest pain, breathlessness, palpitations and fainting.
But a heart trace can often spot the condition.
Dr Barry Maron, of the Minneapolis Heart Institute Foundation, and his team say potential sperm donors could routinely have a heart trace to rule out the condition.
Sperm donors are already screened for genetically transmitted diseases like cystic fibrosis and infections like HIV.
But hypertrophic cardiomyopathy is not included on the list in the US or the UK, although donors are asked about their general heart health.
Dr Maron's team accept that it is not possible to screen for every genetic disease that could be passed on.
"Nevertheless, our observations raise considerations for effective screening strategies to prevent donors from propagating mutant genes that cause relatively common genetic diseases such as hypertrophic cardiomyopathy."
UK expert Dr Allan Pacey, of Sheffield University and the British Fertility Society, said it was an issue that needed debate.
He said: "If you were to consider every disease the list would never end. And some things will always slip through the net.
"But this is something that we should look at as a profession and discuss whether it should be added to the guidelines.
"This case illustrates why we need to be strict about screening donors."
He said the UK had some of the strictest guidelines on sperm and egg donation in the world.
Safeguards include barring men over the age of 40 from donating - they have a higher risk of passing on errors in their sperm that cause conditions such as leukaemia - and only allowing individual sperm donors to give to a maximum of 10 families.
These measures are not in place in the US.
Judy O'Sullivan, cardiac nurse at the British Heart Foundation, did not think sperm donors should be routinely given a heart trace to check for cardiomyopathy.
"We do not support mass screening of the population. But we do help whole families to get screening if one member has been diagnosed with hypertrophic cardiomyopathy."
Dr Jackson Kirkman-Brown, an expert at the Assisted Conception Unit at Birmingham Women's Hospital, said: "Donors are screened carefully, and far more than couples who can just naturally conceive.
"The screening is as rigorous as possible. In general, the vast majority of genetic cases do get picked up.
"You have to balance the screening with the likelihood of the disease being passed on and decide at what level to stop. Otherwise you could have no donors."