Aisha Khan, whose parents are first cousins, has lost siblings to genetic problems

The day her four-year-old brother died is firmly rooted in Aisha Khan’s memory. Aisha was only eight when she woke up to find her home in West Yorkshire filled with people; a kindly uncle scooping her out of bed with her three older siblings while her distraught parents mourned. For months she expected Sarfraz, her tiny brother, to return but she never saw him again.

For Aisha, now 36, the loss was just one of many disasters to befall her family. Her twin brother Ahmed died aged just two-and- a-half. Her elder sister Tahira has serious learning difficulties, and another brother, Kasim, born just two years after Sarfraz’s death, had problems so severe that he required 24-hour care and did not live to see his 18th birthday.

The family’s sadness is unimaginable. Yet the real tragedy is not only that their experience is far from rare, but that it could have been avoided.

Aisha’s Pakistani-born parents, Mohammed and Barkat, are first cousins. There is fresh and growing evidence that marriage between relatives within the Pakistani community may be to blame – in part at least – for a dramatic rise in the number of children with genetic disorders being treated in British hospitals.

Figures obtained by The Mail on Sunday under Freedom of Information laws reveal a huge challenge, not only for such communities, but also for the Health Service. And it comes with vast financial implications.

The figures show that up to 20 per cent of the children treated for congenital problems in cities such as Sheffield, Glasgow and Birmingham are of Pakistani descent, a figure significantly greater than the background populations, which can be four per cent or lower.

Birmingham Children’s Hospital alone has seen the number of Pakistani children treated for genetic disorders increase by as much as 43 per cent since 2011.

Officials admit it is impossible to calculate the cost of treating these problems, but there is no doubting the extraordinary scale of the expense, which even in 2004 was estimated at £2billion a year.

Today that figure will be substantially greater still, as hospitals diagnose an ever broader range of conditions and new treatments become available.

Aisha as a child with her parents Mohammed and her mother Barkat

Scientific studies over at least three decades have linked first-cousin unions to an increased risk of genetic disease.

Yet it remains discussed only with extreme reluctance. Medical professionals fear being labelled racist, while individuals among the groups most affected are reluctant to be seen as disloyal.

Aisha herself is prepared to be criticised by her own community, and is unequivocal in her belief that not only must it accept the latest figures as proof of a growing problem but that action is needed to address it – even if that means taking genetic tests before marriage and in the early stages of pregnancy to prevent further heartbreak.

‘This is a matter of life and death,’ she says. ‘In a climate of casual racism, terror attacks and Brexit, it’s hard to discuss but the Pakistani community must accept these findings. Yes, these conditions can happen to white British people, too, but Pakistanis are more likely to be affected because of generations of inbreeding. Testing means these problems would be less likely to happen.’

Two per cent of the population in the UK is Pakistani or British Pakistani, according to the 2011 Census – just under one million people. Estimates suggest half the marriages are ‘consanguineous’ – between blood relatives – a largely cultural tradition aimed at keeping wealth and property within families. Such marriages are also common in Arab countries and North Africa. This means a disproportionate number of children from these backgrounds are stillborn, die during childhood, or live with lifelong genetic disabilities.

Hundreds of such conditions, many of them so rare they have never before been seen in Britain, are now being diagnosed at children’s hospitals. Typically, the effects include neurological problems, heart or kidney failure, lung and liver failings, blindness, deafness and learning problems.

Perhaps it is an indication of a reluctance to address the issue that there are no collected statistics on the number of disorders linked to consanguineous marriage. We obtained our figures through FoI requests, asking children’s hospitals to break down the number of patients they have seen with genetic disorders by ethnicity.

Officials say it is impossible to calculate the cost of treating these problems, but there is no doubting the scale of the expense, which in 2004 was estimated at £2billion a year

The trend is clear. They show that in Sheffield, for example, 20 per cent of affected children are of Pakistani descent compared with a background population of four per cent. In Glasgow, the proportion is about 18 per cent, even though Pakistanis account for 3.8 per cent of the local population.

In Manchester, Derby and Leeds, about one in ten children with a genetic disorder is of Pakistani heritage – again significantly above the background population. Then there is that extraordinary increase in Pakistani children with genetic disorders in Birmingham – a 42 per cent rise in six years, which cannot be attributed solely to new and better diagnosis of such conditions given that the number of children from a white British background increased by 18 per cent in the same period. Clinicians in the city estimate three-quarters of the Pakistani cases are a result of a first-cousin marriage.

Dramatic as this picture is, the true overall figures could be higher still, as our data does not include statistics from London’s Great Ormond Street, which deals with some of the most complex cases.

The number of children treated there for genetic disorders has jumped by a third in five years. The hospital does not routinely record patient ethnicity but a clinician, who declined to be named, confirmed a significant number of the cases involve first-cousin marriages.

The number of children treated at London's Great Ormond Street hospital has jumped by a third in three years

One of the fundamental stumbling blocks is, controversially, the way that many of those affected interpret their faith.

Aisha grew up in Keighley, where up to 20 per cent of the population is Pakistani and Muslim. Many come from the same few villages in Mirpur, a region now known as ‘Little England’. Aisha broke with tradition by refusing to marry a cousin, so great were her concerns about the risk.

‘My dad would not accept that being married to his cousin could have affected his children,’ she said. ‘He’d say, “The doctors are wrong. It’s in the hands of God.”

‘In his mind, it was all about the will of Allah – nothing to do with genetics, which made me hugely frustrated. He’d say if genetics was the reason, how come some of his children were healthy?

‘Many people I know would say that not marrying a cousin is against our religion. There is a powerful pressure to do so, or risk bringing shame on the family. But it’s a misconception – it isn’t mentioned in the Koran.

‘The community struggles to accept cousin marriages are resulting in difficulties because they think it [marrying outside the family] goes against their faith. I’ve been accused of being Islamophobic or creating problems in the community by raising the issue.’

A study carried out among Pakistani families in Luton in 2015 found that Aisha’s father is not alone in his views. The infant mortality rate is a staggering 63 per cent higher in the town than the national average, and is at its highest in the Pakistani community.

But a majority of those questioned had a limited understanding of genetic risk – even those in contact with specialists because of an affected child – and ‘disputed the evidence of the link’ between first-cousin marriages and birth defects.

Aisha's younger brother Sarfraz who died in 1988

It is telling that the Muslim Women’s Network has received no calls to its helpline on the issue.

Callers do, however, ring regularly about subjects including forced marriage and female genital mutilation.

So great is the fear of being branded racists, most of the hospitals and local authorities approached to talk about the issue refused to do so. But orthopaedic surgeon Dr Suhail Chughtai, himself a Pakistani, said he had witnessed ‘terrible problems’ among his own family and friends.

‘There is a problem of segregation among Pakistanis who have moved to the UK, of not looking beyond their community.

‘The country they came from has moved on, but they haven’t benefited from that cultural revolution. And they haven’t benefited from their new country because they’re stuck within their own people.’

This denial exacts a destructive human cost, which is as inevitable as the laws of genetics.

While everyone carries the occasional copy of a faulty gene, the damage to any offspring is caused only when faulty genes come together as a pair. And because those who are related to each other are more likely to carry the same faults in their DNA, their children are at a much greater risk of inheriting not just one copy of a faulty gene, but two – one from each parent.

I've been accused of Islamophobia but we must talk about it

It means that, for each first-cousin pregnancy, there is a one-in-four chance of having a child with defects.

A groundbreaking study, Born In Bradford, successfully raised the issue in 2013. It found cousins who married were twice as likely to have a disabled child compared to those in non-cousin marriages. Such unions also accounted for nearly a third of all birth defects in babies of Pakistani origin.

Geneticist Professor Steve Jones, from University College London, said: ‘If you walk up to someone in the street with European ancestry and shake their hand, there’s a one in two chance that person is your fifth cousin. In other words, you share an ancestor who lived around the same time as Charles Darwin.

‘If you’re Pakistani and you do this in Pakistan, there’s a one in two chance they’re a second cousin. There have been cousin marriages in Pakistan for a long, long time. Within one generation there are fewer issues; following many generations there are a lot.’

However, he added: ‘It’s important to put it into context – the risk is equivalent to women over the age of 34 getting pregnant.’

Ann Cryer, Labour MP for Keighley until standing down in 2010, is among those who have campaigned for greater awareness. She has described the cases she saw as ‘constant and heartbreaking’.

‘One middle-class family had six children with two healthy girls, and four disabled boys between toddler age and 11 who needed hoists to move,’ she said. ‘And yet the mother-in-law had thrown away their contraceptive pills and was pressuring them to have more children so they could have a “perfect” son. One doctor was dismissed by another woman’s mother-in-law, who told him, “The reason she’s having these children with difficulties is because life in the West is not appropriate – it’s the will of Allah, and you’re a bad doctor.”

Former Labour MP Ann Cryer has campaigned for greater awareness of the risks

‘No one dared talk about it. If you’re white, it’s seen as racist; if you’re Pakistani, you’re disloyal. If you’re going to marry your first cousin, get tested or screened for genetic compatibility first.’

There are signs of progress. Important work is being carried out by Birmingham Women’s and Children’s NHS Foundation Trust, for example. Dr Saikat Santra, a consultant in metabolic disorders at Birmingham Children’s Hospital, describes how local imams are playing a part, advising families that, in some interpretations of the Koran, the soul only enters the foetus at 100 days, which means that they are allowed to seek early pre-natal testing and, potentially, abortion.

Dr Santra said families are now more willing to seek advice on genetics. However, even testing before marriage is not by itself sufficient, according to Jenny Morton, a consultant clinical geneticist based at Birmingham Women’s Hospital, who said that only certain major problems can be detected this way. Other measures might be necessary too, including early pregnancy screening.

‘A misconception is that these families don’t want to hear about genetics,’ said Dr Morton. ‘What they don’t want to hear is that they’re doing things wrong – that’s when they withdraw. We have had a high non-attendance rate at our clinics among Pakistani families because they didn’t understand why they were being sent for and thought we were going to tell them what to do.’

There was pressure on one family to have a perfect son

It could be, also, that a change to British immigration laws is helping reduce the number of problems produced between cousins.

Professor Neil Small, one of the Born In Bradford researchers, said: ‘We’ve changed the law to introduce an income threshold for spouses coming in from outside the EU, and the experience of other countries such as Denmark and Norway would suggest that could produce a fall in intercontinental marriage generally. The anecdotal evidence suggests it may already be true.

‘Cousins have historically been brought in from places like Pakistan to marry. But this is now more difficult to do.’

Aisha, too, believes society may be on the cusp of change. ‘Five or ten years ago, no one would have questioned cousin marriage. But my brother and sister-in-law, who are cousins, thought long and hard about having a fourth child because they knew the risk.

‘This is progress. More have to talk about it. That’s key. I’ve had three siblings die. If my parents had known, maybe we could have avoided that.’