Parents who are blood relatives and older mums are the two main causes for Bradford’s birth defect rate being twice the national average, according to new research.

Scientists have analysed data provided by 11,396 mums and youngsters involved in the Born in Bradford (BiB) study of children born at Bradford Royal Infirmary between 2007 and 2011.

They found that while 1.7 per cent of babies across England and Wales are born with a birth defect, that figure was three per cent in Bradford.

Their research, published today, found the risk of a child being born with a genetic anomaly rose from three per cent to six per cent if they were born to blood relatives, which accounts for three-quarters of marriages among families of Pakistani descent in the city.

And age was another major factor, with the likelihood of having a child with a genetic defect doubling from two per cent among white British mums aged between 25 and 34, to four per cent among those aged over 34.

However, they found factors such as smoking, alcohol consumption, obesity and blood sugar control during pregnancy did not appear to add to the risk – findings that were greeted with concern by the chairman of Bradford Council health scrutiny committee.

Of the families studied by BiB researchers, 386 had children with genetic conditions, including heart and lung problems and syndromes like Down’s, or genetic mutations like extra fingers and toes.

Figures show 37 per cent of Pakistani mothers involved in Born in Bradford are married to first cousins and 63 per cent are married to blood relatives.

In the Pakistani subgroup, which accounts for about 45 per cent of families involved in the project, 77 per cent of babies with birth defects were born to parents in consanguineous marriages.

And of the white British cohort, 19 per cent of babies born with a genetic defect were to women aged over 34.

Researchers say the study is the first that has been able to explore the potential causes of birth defects in a population where there are enough numbers in both consanguineous and non-consanguineous to reach “reliable and statistically significant” conclusions.

Bradford University Professor Neil Small, the co-author of the study, said: “This research is of particular importance to Bradford because of the characteristics of its population.

“Half the babies born in the city’s one maternity hospital have a parent whose family origins are in Pakistan.

“But the findings also have relevance to other areas of the UK and across the world in countries where consanguineous marriage is a cultural norm.

“In Bradford, there are initiatives that seek to raise community awareness and services such as genetic counselling and testing in place that can be accessed by couples who are married or considering marriage to a blood relative.

“It is not our intention to counsel couples about who they choose to marry, but we do want to ensure that couples are aware of any risks so they can make informed decisions when planning their families.”

Geneticist and lead author of the paper, Dr Eamonn Sheridan, of the University of Leeds, said the information showed the need to develop more family-centred genetic services and hoped it would raise awareness of risk factors.

“Although there is an increase in the risk factor for babies born to mums married to first cousins, 94 out of 100 of those don’t have any genetic anomaly and are fit, well and healthy,” he added.

Councillor Mike Gibbons, chairman of Bradford Council's health overview and scrutiny committee, said he had yet to read the report, but the number of children born with birth defects in Bradford does have an impact on the cost of health services in the district.

“The cost of health and social care services increases with genetic problems and anything that can be done to help recognise these problems can have an impact on that outlay,” he said.

“Obviously these findings will be looked on with keen interest by health professionals in Bradford and Leeds.

“It’s been recognised for some time that there are problems in the Bradford area and it would be in everyone’s interests if the problems that have been identified can be addressed as soon as possible.”

But he expressed concerns about the findings that suggested drinking, smoking and obesity did not increase the risk of birth defects, saying: “I find it interesting that these findings seem to go against the current advice regarding these matters.

“I would caution people to heed the previous advice because I think the benefits of not drinking and not smoking are clear and have been seen to produce a much healthier lifestyle.”

Researchers say it has been known for some time that birth defects are a major cause of infant mortality and their incidence varies across ethnic groups.

And other studies in the last 20 years considering marriage to a blood relation as a cause have been unable to rule out other potential risk factors, including deprivation.

But the team found that levels of deprivation had no effect on the relative risk of birth defects, despite two-thirds of the mothers taking part in the study coming from the most deprived fifth of the British population.

And, according to the data, mothers educated to degree level halved the risk of having a baby with a congenital anomaly.

This was across all ethnic groups in the Born in Bradford cohort, which includes 43 different ethnicities – 45 per cent Pakistani and just under 40 per cent white British.

One Bradford GP, Rafaqut Rashid, a member of Bradford’s City Clinical Commissioning Group, said the link between consanguineous marriage and genetic disorders had often been ‘poorly understood’ and information from the study could be used to shape health services in the district.

The NHS in Bradford and Airedale said it is increasing awareness of genetic disorders by making it a key action point in its Every Child Matters strategy and has set up a steering group to look at how families can be informed about potential risks.

“It is something that is already on the agenda, but this reinforces the need to promote initiatives to create greater understanding and openness about genetics among the public and health professionals,” said Dr Rashid.

“I want to make sure this information leads to something positive in Bradford in maternity care and genetic services.”

And Dr Peter Corry, a recently-retired consultant, who worked in the Child Development Centre at Bradford Royal Infirmary for 25 years, added: “I’m pleased there’s more awareness.

“People have known for some time that genetic conditions are more common in communities who marry within themselves or are more isolated.”

Dr Shirley Brierley, consultant in public health at Bradford Council, added: “This is important research as it will inform our work around raising awareness of congenital anomalies among all communities in Bradford.

“It will also help to guide how we engage with families which have a higher risk of inherited disorders so they can understand fully the risk of a baby carrying such a disorder and the support available to help them make informed choices.”

The study was funded by the National Institute for Health Research under the Collaboration for Leadership in Applied Health Research and Care programme.