Marriage between first cousins 'doubles risk of having baby with life-threatening birth defects'

Children born to parents who were not cousins but were closely related also had an increased risk

Marriage between first cousins more than doubles the chance of having a baby with potentially life-threatening birth defects, a study of births in Bradford has revealed.

From a sample of nearly 11,000 births between 2007 and 2011, more than 2,000 babies were born to first cousin parents – predominately from the city’s large Pakistani population. The children of such unions, which represented more than a third of all the Pakistani-origin babies in the study, had a six per cent chance of having a congenital abnormality, compared to an average 3 per cent chance.

Children born to parents who were not cousins but were closely related also had an increased risk. Overall the number of birth defects in Bradford was more than double the UK average – which stands at 1.7 per cent. Researchers said that pre-natal health services in cities with large Pakistani populations should include advice on the risks of marrying close family members.

A link between cousin marriage and health problems– including heart and lung problems and recognised syndromes such as Down’s – linked to genetic inheritance, has been observed in communities around the world. More than one billion people live in communities where the practice is commonplace. Only one per cent of unions in the UK are between cousins, but in Bradford that figure is much higher – 18 per cent of unions, and 37 per cent of those within the Pakistani community.

The new “Born in Bradford” study, published in The Lancet today, is largest of its type and the first in the UK to take into account the effect of socio-economic factors, age and lifestyle factors the prevalence of birth defects, in order to isolate the impact that cousin marriage – or consanguinity.

Nearly a third (31 per cent) of birth defects in Pakistani origin babies could be attributed to marriage between blood relatives, researchers from the University of Bradford and the University of Leeds said, but they stressed that the absolute increase in risk was small.

“At the heart of all this is children that are being born with often very distressing illnesses,” said Professor Neil Small, of the University of Bradford. “Many of these things are preventable, what we hope our paper does is contribute to a debate that means that in the future, some of them will be prevented. We customarily offer pre-conception and ante-natal advice that looks at areas like maternal age and health-related behaviours such as smoking, alcohol consumption. We think that in areas with high levels of consanguinity we could add to that health promotion package information about the risks associated with cousin marriage.”

Dr Rafaqut Rashid, a Bradford GP, said that there was already awareness within the community about the risks of cousin marriage.

“Different families will take on this advice in different ways. Patients should be given an informed choice,” he said. “We don’t want to force anything on patients. They will measure what’s beneficial for them. That’s not for us to dictate.

“Families tend to weigh the benefits in accordance to the advice you give them. Patients often recognise social benefits to cousin marriages: extended families, social stability, marital stability,” he added.