Consanguineous marriage, or marriage to a blood relative, is a custom that has been popularly practised in almost every part of the world at some point of time. Though in the West it has largely grown out of the culture and become stigmatised, in many other countries, like Oman, it continues to remain a valued social custom.
In fact, according to Professor Alan Bittles, a professor of community genetics at Edith Cowan University and research leader in the centre for comparative genomics at Murdoch University, both in Australia, it is estimated that ten per cent of marriages worldwide are consanguineous. In regions where consanguineous marriage is more popular such as the Middle East, North Africa and Central and South Asia, the number can reach over 50 per cent, and in countries like Qatar and the UAE it is said to be on the rise.
Nevertheless consanguineous marriage and the genetic implications for children of such marriages, is a controversial subject. While some politicians, media and experts in the field have warned against the greatly increased health risk of consanguineous marriage, many scientists claim they are vastly misguided, and at the same time completely disregarding the social significance of the practice.
“There is a misunderstanding spread by the media that there is a risk from consanguineous marriages, but this is actually very minimal,” said Dr Allal Ouhtit, head of the department of genetics at Sultan Qaboos University (SQU).
Though current research estimates that there is double the risk of mortality and disability for a child if its parents are first cousins, this only increases from about two to four per cent - still leaving around a 96 per cent chance that the child will be healthy.
“Even still, we are not sure because research on consanguinity has bought conflicting results. All the studies have been done in the West and were probably not well controlled. That's why we are trying to set research up here,” added Dr Allal.
“Our findings have shown that the health risks associated with consanguineous marriage have been exaggerated, largely due to flawed research,” agreed Prof Alan , who visited Oman recently to participate in the International Conference on Consanguinity. “Research has often failed to allow for non-genetic factors that can adversely influence health outcomes including poverty, poor maternal health, very young maternal age and short intervals between births.
“There has been a tendency to blame all adverse health outcomes on consanguinity, when in fact it would be expected only to influence the prevalence of inherited disorders that are rare in the general population. So, for example, it would not be expected that consanguinity would have any major impact on common disorders such as beta-thelassaemia in Oman.”
Of course, in families who carry a genetic disease, the chances of passing the gene on are much higher. But nowadays genetic screening can detect health risks. In Oman, pre-marital genetic screening is widely available and encouraged, although stigma and perhaps fear means it has yet to be adopted by the major-ity of the population – according to the Ministry of Health, approximat-ely only ten per cent of the population has undergone the test.
“Since many diseases appear in many Omani families, we highly recommend pre-marital check-ups,” said Ahlam Barwani, a member of the Oman Hereditary Blood Disorder Association (OHBDA), which has run various campaigns to promote pre-marital screening. “It is not forced on you to marry within a family. On the other side, sometimes people from totally different families can have offspring born with a disease. If you believe there is a high risk of passing defective genes to your offspring you can avoid it. Otherwise go for the blood test.”
Meanwhile, regional research is continuing. Dr Allal and his team are pushing for more awareness on consanguinity and prevention methods including pre-implantation genetic diagnosis, which screens for genetic diseases in embryos prior to implantation. Others are using less obvious research techniques - archaeologists in the area have been extracting DNA from ancient bones and comparing them to DNA from the current population in order to trace diseases.
“What is important from a scientist’s point of view is that we need to build a research culture here,” said Dr Allal. “There has been huge progress in technology and we need to use the tools to develop. If there is a risk, and we believe there is a minimal risk, we can then develop prevention.”