Consanguineous marriage is defined as the union of two individuals who are closely related such as first cousins or uncle & niece.
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This type of union is preferred among some communities in India, the Middle East, and North Africa. There are several reasons why consanguineous unions are favored. By marrying within the family, it is expected that the bond between the family members grow stronger. For any women’s parents, such marriages mean that their daughter will have a better relationship with her in-laws and that she will probably be close by. It also helps maintain the property within the family.
Risk from Consanguineous Marriages
However, with such marriages comes certain risk in terms of genetics i.e. the offspring from such a union is at an increased risk for autosomal recessive (AR) disorders such as Cystic Fibrosis, Beta Thalassemia, Sickle Cell Anaemia, etc. In other words, offspring from a first cousin marriage is at 1.7 – 2.8% increased risk for inheriting a specific genetic disorder compared to the general population.
An individual who seems to be normal will have two functional copies of each gene. This gene codes for a specific protein which in turn carries out a specific function. In some cases, a couple will be carrying one defective copy each giving them the carrier status for that disorder. When both the genes are defective then that individual will manifest the disorder as seen in AR disorders. When there is a history of consanguineous marriage in a given family, the chances of having an AR disorder increases because individuals belonging to the same extended family share common genetic regions.
Genetic testing options available to screen for genetic disorders
With recent advancements in genetic testing, it is now possible to identify if a couple is at risk for passing on an AR disorder. One such genetic test offered is Carrier Screening Test, this test can detect if a couple is a carrier for the same AR disorder. It is a next-generation sequencing technique where each gene is sequenced to look for a common mutation between the couple. As with all genetic tests, pre-test and post-test genetic counseling is essential. During pre-test counseling sessions, the couple will be counseled on the pros and cons of the test and what sort of result they can expect. In a post-test counseling session, the couple is counseled on the significance of their result and what should be their next course of action.
In case common mutations are detected, prenatal diagnosis (testing the fetus) or IVF with Preimplantation Genetic Diagnosis (PGD) or the need for donor egg/sperm can be offered. Taking several factors into consideration, the course of action varies from one couple to another. Facilities such as preconception genetic counseling (offered for couples who are planning on starting a family) and premarital counseling (offered for couples before their marriage) are accessible.
Consanguineous marriages involve certain genetic risks but with the help of appropriate knowledge and support, the risk can be identified and managed.
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