WA scientists are challenging the myth that inbreeding always leads to unhealthy babies.
The highly contentious, often-tabooed practice has in the past been linked to deformities such as heart disease, mental retardation, deafness and even blindness.
Australian research published in 2001 showed that babies born to first-cousins are nearly three times more likely to have serious birth defects.
But Professor Alan Bittles, an adjunct professor at the Centre for Comparative Genomics at Murdoch University, who has spent 30 years researching the topic says most children born to first-cousins are healthy.
In WA, about 500 marriages are between first-cousins.
“In Western culture there is a general belief that first cousin marriages lead to negative genetic outcomes, yet a large majority of children born to first cousins are healthy,” he said.
Prof Bittles reviewed 48 studies from 11 countries and found that the risks of birth defects rose from about 2 per cent in the general population to 4 per cent in consanguineous or same blood couples.
He found that only 1.2 per cent suffered higher infant mortality rates, a find similar to another review from 2002 that suggested first-cousin children are less than 3 per cent more likely to have genetic deformities.
The issue has sparked a major medical debate with some researchers and politicians claiming inbreeding between first-cousins in UK has led to a rise in rare recessive disorders – many of them fatal.
Prof. Bittles was the lead speaker at the Royal Society of Medicine in East London this week where these divisions were hotly disputed.
Speakers at the event argued that warnings on the negative genetic consequences of such unions should be as prominent as alcohol and tobacco cautions.
Einstein and Darwin married their first-cousins, so did Jerry Lee Lewis and Jessie James and according to Prof. Bittles about 500 West Australians have followed suit.
First-cousin marriages are also a common tradition in countries such as Pakistan, south Asia and the Middle East.
Muslim doctors at the East London debate agreed with Prof. Bittles and suggested the risk of birth defects is only 4 per cent higher for parents who are closely related – making it ‘not likely’ there will be a genetic problem.
“There is widespread misconception that these marriages rare,” Prof. Bittles said.
“In reality there are over 1000 million people worldwide that live in regions where 20 – 50 per cent of marriages are between blood relatives.”
Prof. Bittles believes as more migrants move into Australian communities there will be a greater incidence of first-cousin marriages.
Given the large numbers of cousin marriages Prof. Bittles is calling for more in-depth health-based studies on the issue.