Cousin marriages: a question of understanding

A lot has been said on the issue of marriages between cousins and its potential genetic risks since the airing of Channel 4's Dispatches: When Cousins Marry last month. Feedback has been both positive and negative, but different extrapolations of the true picture have complicated understanding around this issue by stigmatising certain communities and highlighting unrelated issues such as immigration, religion or politics.

The fact remains that this is a health issue, which has lead to a higher than normal infant and perinatal mortality in cities such as Birmingham and Bradford. The extent of the morbidity is not yet known, but a fair indication can be found in the rise in the number of applications for disability living allowances for children in these areas. A disproportionate number of cases occur among those of south Asian, and especially Pakistani descent, but it can affect all ethnicities and should be a concern for all. It is time to discuss it rationally so we can enable informed reproductive choices.

The genetics of cousin marriages are fairly simple. There is a 2-3% risk of rare recessive genetic disorders in unrelated couples for every pregnancy. This risk rises to 4-6% in first-cousin marriages but higher if there is persistent practice of first-cousin marriages over the generations. We all carry mutations in our genome – the genetic code that carries the blueprints for our body, half of which we get from our fathers and the other half from our mothers. The chances of both carrying the same mutations is low, but is higher in first cousins and those marrying in very close-knit communities. If they both have the same mutations, there is a one in four chance of having an affected child – which can mean anything from a mild to a catastrophic illness, or even a miscarriage. More importantly, there is a one in two chance of having children who, while unaffected themselves, are also carriers.

Cousin couples who do have a healthy baby can be the victims of a false sense of genetic security, which could encourage unions without premarital or preconception testing. The best prevention strategy, together with counselling, is to avoid first-cousin marriages or those within insular communities, as we can't test for all rare genetic conditions.

As GPs, we see the consequences of such unions. They are distressing not only to the affected child, but also to the siblings, parents and extended family. One of the parents often becomes a full-time carer, which leads to financial difficulties and related emotional ailments. This is in addition to the anguish of being given such devastating news during pregnancy and the numerous hospital treatments the child has to undergo. No one questions the right of individuals to make their own reproductive choices, but these should be informed.

With the above in mind, Birmingham has embarked on an initiative to provide education to our residents. The Enhanced Genetics Services Project aims to provide a multi-strand approach to reduce the increasing infant mortality in the city. The initiative will look at reviewing past patients and new technologies available to deal with their illness, as well as developing new tests for such conditions. However, the paramount concern is the education of patients, healthcare professionals and the community as a whole.

Three practices across Birmingham currently offer screening for the blood disorders thalassaemia and sickle cell anaemia to all patients over 16 years of age. Those found to be carriers are counselled and a more detailed discussion of genetic risk undertaken. They are also searching records for patients known to have genetic diseases, in order to offer them counselling. It is at this stage that the education of genetic risk is undertaken, and this has also led to the development of a genetic register, which aids identifying families who would benefit from such services.

As GPs, our rapport and trust with patients, whose family dynamics we are often familiar with, puts us in a unique position to impart such education in a nonpolitical and effective manner. When we take into account the sensitivities and feelings of our patients and community, this education is likely to be more effective. There are, however, several barriers to such services, including some cultural beliefs and political arguments. Within the communities most affected there are often concepts of fate or the will of God, which can be discussed on an individual basis. A non-judgmental approach is the key to this process, as is the support of other community leaders such as clergy, community workers and so on.

Success is hard to gauge at such an infancy stage, and often requires a few decades, as it involves a cultural shift. We are, however, seeing more willingness to participate in genetic risk assessments, counselling and an interest in taking up genetic testing in pregnancy. This is a small measure of progress so far, but the time for action is now.
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References:

Alidina, Rizwan, Walji, Mohamed. 2010. "Cousin marriages: a question of understanding". Guardian. Posted: September 17, 2010. Available online: http://www.guardian.co.uk/commentisfree/2010/sep/17/cousin-marriages-understanding-health-risks