Cousin marriage and autosomal recessive conditions – what is the best approach?

Corinna Alberg

15 October 2015

Marriage between cousins is a traditional practice in many parts of the world, helping to strengthen family ties and ensuring that wealth stays within the family. Perhaps more importantly cousin marriage can provide protection for women who are likely to have a higher social standing living with their own extended family rather than living as part of a family to which they were not related. For most consanguineous marriages (usually defined as the marriage of a second cousin or closer relative), there are no adverse health consequences for offspring, but where there is a recessive condition in the family, cousin marriages increase the risk to a child. As a result, for some families consanguineous marriages can result in one or more children developing serious, even life-threatening conditions.

Inherited recessive diseases

When a child with a recessive condition is born to a family where the parents are related, it is essential this is followed up. On diagnosis, clinical services need to ask the parents whether they are related or part of the same wider kinship group. In many communities of Pakistani origin, the majority of marriages are between individuals from within the same biraderi. The biraderi is a network of individuals with common ancestry; even if the parents are not cousins they may have some level of relatedness. So, to assess the risk for future children, it is important to establish not only if both parents are closely related but also if they are from the same kinship group. Those who report being second cousins may actually be more closely related if cousin marriages have taken place over successive generations. If relatedness is reported, then the offer of genetic testing should be made to identify whether both parents are carriers of the child’s disorder - reproductive options such as prenatal screening for future pregnancies can then be offered. This also has implications for the wider family and genetic testing should be offered to other at risk family members.

The Enhanced Genetic Services Project in Birmingham

A recent project in Birmingham, the Enhanced Genetics Services Project (EGSP) was prompted by rates of infant mortality much higher than the England and Wales average. The EGSP report identified that half of mothers of Pakistani origin were married to a relative, compared to 1% of the white European mothers. Underlining the importance of the initiative, the combined stillbirth and infant death rate due to autosomal recessive congenital anomalies for Pakistani mothers was almost forty times higher than that for white European mothers. Two thirds of infant deaths suffered by Pakistani mothers were due to congenital anomaly causes compared to 7% among white European mothers.

Local community views of the health consequences of consanguinity in Luton

High rates of stillbirth, infant mortality and genetic disorders in Luton have also led to a local study of the health impact of consanguinity. The researchers note that, in Luton, Pakistani babies account for almost a third of babies born with autosomal recessive conditions. They examined the perceptions of the Pakistani / Kashmiri community of the health risks associated with consanguineous marriages.

The majority of those interviewed in Luton had minimal understanding of genetics. A minority had discussed cousin marriage and genetic risk with their doctor; however, at the insistence of the patient, these conversations had been short. Most disputed that consanguineous marriage is linked to genetic risk, arguing that the birth of disabled children in non-consanguineous families undermined the link. The researchers noted that the stigma of having a child with a disability led to an avoidance of discussing details of such children, but the participants were very open to receiving more information on the risks of genetic disorders related to consanguinity.

The way forward

A conclusion from both of these projects is that the way the offer of genetic counselling and testing is made is very important. In Birmingham, the EGSP encountered little resistance to its focus on consanguinity and genetic risk. Learning from a previous, poorly received initiative, a central precept for the project was to offer the service in a sensitive manner so families did not feel they were being blamed for the birth of a sick child. Another sensitive area is how to encourage parents to share information about their child’s condition with other family members. This is in a context where notions of ‘good blood’ are important to arranging marriages as well as a lack of understanding of genetics and problematic family dynamics, both of which are common to all parts of society but inhibit sharing information.

Information sharing

The authors of the Luton study note the importance of using evidence of good practice from other areas of the UK to address the issue and deliver culturally sensitive services. Tower Hamlets’ joint strategic needs assessment for 2014 -15 also highlighted the need to liaise with other regions in England where activities have been undertaken on this topic.

When discussing these issues with health care providers from the UK and internationally there is a strong desire to work with communities in a culturally sensitive manner. There is a pressing need to share learning from studies and pilot programmes so that services can be developed that are more likely to be acceptable to the communities they aim to serve. The theme of needing to share information comes up time and time again in the policy work undertaken by the PHG Foundation. For a variety of reasons, institutions, projects and individuals seem to be unwilling to share data, yet sharing information whether to aid the interpretation of genomic data to maximise clinical utility of genomic test results or on how best to deliver services is key to improving health outcomes for individuals and populations.