In a busy, terraced house in Bradford, three sisters are animatedly chatting. It's a big day at their home: a beautician sits on their sofa, styling their hair and makeup. The room is warm with fun and laughter. It feels like a scene from a Jane Austen novel: three women in their late 20s, each of them bursting with personality, swapping stories.And like most Austen novels, the conversation often turns to marriage.The sisters are preparing for a family wedding at the weekend - where the bride and groom are first cousins. Many people might find this unusual, but in their family and in some parts of Bradford, it's fairly common.Ayesha, who at 29 is the oldest of the three sisters, also married her first cousin in 2017. She has two children with her husband and their marriage is happy, she says. It felt perfectly normal at the time to marry her cousin. Their mother, a Pakistani migrant, assumed it was what all three of her daughters would do.But 26-year-old Salina, the youngest of the three, tells us she broke the mould by having what they call a "love" marriage, choosing a partner from outside the family. Salina tells us she is outgoing and ambitious; marrying a cousin simply did not appeal to her. Then there's Mallika, who at 27 is the middle of the three. She's still single and has already decided not to marry within her family."I said to my mum that I wouldn't judge my sisters but I wasn't going to do it," Mallika tells us. She says having an education has created opportunities for her. "Before, even if you had an education, you wouldn't be expected to carry on with it. You would be thinking of marriage. Now the mindset is so different."Worrying new dataIn the UK and across Europe, cousin marriage is coming under increased scrutiny - particularly from doctors, who warn that children of first cousins are more likely to experience an array of health problems.
And there's now some new, potentially worrying data from Bradford to add into that mix.
Researchers at the city's university are entering their 18th year of the
Born in Bradford study. It's one of the biggest medical trials of its kind: between 2007 and 2010, researchers recruited more than 13,000 babies in the city and then followed them closely from childhood into adolescence and now into early adulthood. More than one in six children in the study have parents who are first cousins, mostly from Bradford's Pakistani community, making it among the world's most valuable studies of the health impacts of cousin marriage.
And in data published in the last few months - and analysed in an upcoming episode of BBC Radio 4's Born in Bradford series - the researchers found that first cousin-parentage may have wider consequences than previously thought.
The most obvious way that a pair of blood-related parents might increase health risks for a child is through a recessive disorder, like cystic fibrosis or sickle cell disease. According to the classic theory of genetics laid out by the biologist Gregor Mendel, if both parents carry a recessive gene then there's a one in four chance that their child will inherit the condition. And when parents are cousins, they're more likely to both be carriers. A child of first cousins carries a 6% chance of inheriting a recessive disorder, compared to 3% for the general population.
But the Bradford study took a much broader view - and sheds fresh light. The researchers weren't just looking at whether a child had been diagnosed with a specific recessive disorder. Instead they studied dozens of data points, observing everything from the children's speech and language development to their frequency of healthcare to their performance at school. Then they used a mathematical model to try to eliminate the impacts of poverty and parental education - so they could focus squarely on the impact on "consanguinity", the scientific word for having parents who are related.
A series of three bar charts showing modelled outcomes for children whose parents were first cousins compared with children whose parents were not related, based on the Born in Bradford study. Children of first cousins had a lower probability of reaching a good stage of development in the early years’ foundation profile (53.7% compared with 64%), and a higher probability of being diagnosed with speech and language learning difficulties (11.3% compared with 7.4%). They were also predicted to attend 4.1 primary care appointments per year on average, compared with 3 for children whose parents were not related.
They found that even after factors like poverty were controlled for, a child of first cousins in Bradford had an 11% probability of being diagnosed with a speech and language problem, versus 7% for children whose parents are not related.
They also found a child of first cousins has a 54% chance of reaching a "good stage of development" (a government assessment given to all five year-olds in England), versus 64% for children whose parents are not related.
We get further insight into their poorer health through the number of visits to the GP. Children of first cousins have a third more primary care appointments than children whose parents are not related - an average of four instead of three a year.
What is notable is that even once you account for the children in that group who already have a diagnosed recessive disorder, the figures suggest consanguinity may be affecting even those children who don't have a diagnosable recessive disorder.
Neil Small, emeritus professor at the University of Bradford and the author of the study, says that even if all of the children with recessive disorders visited their GP more than average, "this does not explain the much wider distribution of excess health care usage in the consanguineous children".
The study, he says, is "exciting because it gives the opportunity for a much more accurate development of a response, targeting interventions and treatments".
It is, of course, just one study, and the population of Bradford is not representative of the whole of the UK.
Nevertheless, it adds to a growing concern among scientists that has caught the attention of lawmakers across Europe. Two Scandinavian countries have now moved to outlaw cousin marriage entirely. In Norway, the practice became illegal last year; in Sweden, a ban will come into effect next year.
Richard Holden (pictured) has proposed a private members' bill to make the practice illegal, adding it to the list of banned marriages
In the UK, the
Conservative MP Richard Holden has introduced a private members' bill to outlaw the practice, adding it to the list of illegal marriages (alongside parents, child, siblings, and grandparents). But the Labour government says there are "no plans" to impose a ban. At present, the UK is still following the policy of "genetic counselling", in which first cousin-couples are educated about the risks of having children, and encouraged to get extra screening in pregnancy.
But amid concern about child health and strains on the NHS, some academics are asking whether a beefed-up approach to counselling is needed, with more funding and laser-focused intervention. And there are those who think it's time to follow the Scandinavian example and impose something bound to be difficult and controversial: an outright ban on cousin marriage.
For most in the UK, the prospect of marrying a cousin is largely alien. But it wasn't always so unusual. The father of evolution Charles Darwin married his first cousin, Emma Wedgwood. Their son, the Victorian scientist Sir George Darwin, went on to estimate that cousin marriages accounted for almost one in 20 aristocratic unions in 19th Century Britain. One of them was Queen Victoria, who married her first cousin, Prince Albert. The novel Wuthering Heights is full of fictional examples.
Consanguineous marriage remains relatively common among some South Asian communities
By the 20th Century the proportion of marriages between cousins had declined to about 1%. But it remains a relatively common practice among
some South Asian minorities. In three inner-city Bradford wards, almost half (46%) of mothers from the Pakistani community were married to a first or second cousin, according to the most recent Born in Bradford data published two years ago.
For those who want to ban the practice, the public health argument is compelling. When announcing his private members' bill in December, Richard Holden highlighted the higher risk of birth defects. Later, on Talk TV, he pointed to data showing that infant mortality rates are higher for children born to cousin parents, with more heart, brain, and kidney problems due to recessive disorders. He also explained that health effects can be "compounded" when the practice persists through generations.
This risk to child health is one of the reasons Patrick Nash, a researcher and co-founder at the Pharos Foundation research institute, wants to see cousin marriage banned. In a paper published in the Oxford Journal of Law and Religion last year, Nash wrote that a ban would result in "immediate" health improvements, especially in communities where the practice is common. He said: "Banning cousin marriage would improve public health drastically and have no negative health implications of its own."
Prof Sam Oddie has worked in Bradford for over 20 years and has witnessed many cases of severe genetic disorders
On the ground in Bradford, it's a more mixed picture. Prof Sam Oddie, a consultant neonatologist and researcher at Bradford Teachings Hospitals, has worked in the city for more than two decades. Over the years he has observed lots of severe genetic disorders. "I've seen fatal skin conditions, fatal brain conditions, fatal muscle conditions". He says it was "immediately clear" these conditions were occurring more in Bradford than elsewhere.
He remembers some tragic examples: families who lost several children, one after the other, to the same genetic disorder. "That's very upsetting and very difficult for the family to get their heads around."
Common ancestors
But crucially, Prof Oddie thinks the main risk to genetic health in Bradford is not cousin marriage, but a similar issue known as endogamy, in which people marry members of their close community. In a tight-knit ethnic group, people are more likely to share common ancestors and genes - whether or not they are first cousins, he says.
Endogamy is not unique to Pakistani communities in the UK. It is an issue too in the UK's Jewish community and globally among the Amish and also French Canadians.
"It's often the case that the exact familial tie can't be traced, but the gene occurs more commonly within a certain group, and for that reason, both parents carry the affected gene," Prof Oddie says. "It's an oversimplification to say that cousin marriage is the root of all excess recessive disorders in Bradford or in Pakistani communities. Endogamy is an important feature."
The power of education
Rather than a ban, he stresses the power of education - or what he calls "genetic literacy". It's a phrase that crops up again and again from the people we speak to. For many years there's been a campaign in Bradford to inform people in the Pakistani community about their genetic risks. Couples are given specialist advice at their GP; at pregnancy classes, information is shared with expectant mothers.
Bradford has long run campaigns to raise awareness of genetic risks within the Pakistani community
And in Bradford at least, some are taking the message on board. Back at the sisters' house, all three women we interview say that ideas around cousin marriage are slowly changing, in part due to an increased awareness of health risks. They live in the deprived, post-industrial Manningham area of the city. There's a distinct feeling of neighbourliness here. All of the front doors open directly onto the street, which is full of children playing. Occasionally the sounds of their laughter drift inside.
"It has to be something that happens gradually - it's slow, you can't rush it," says Salina, the sister who chose to have a love marriage. "My mum was very young when she came [to the UK from Pakistan]. She had certain views but those changed because she loves us. I just explained to her, 'Mum, how does it benefit you to push cousin marriage?'."
Mallika, her older sister, agrees. "It's also to do with social media and being exposed to different people," she says. "You have new connections... contact with people outside our parents' eyes."
Even Ayesha, the oldest sister who is in a cousin marriage, said she doesn't imagine either of her two children will marry their cousins.
At the time she married her cousin, she says, "I didn't know any different. My parents were strong in their culture. As the generations move on, the culture is disappearing a bit."
She was aware of the genetic risks when she had her two children. Neither of them have a genetic illness.
"We did take that on board," she says, on the topic of genetic health. "But I always feel like if it's going to happen, it's going to happen. If the child is going to be born with a disability then it will happen if you are married to a cousin or not."
