Why you should not marry your cousin

Miscarriages, still-born babies, mutations, diseases - inter-family marriages pose a grave danger.

Nida Hasan October 05, 2011
Doctors are often looked up to, and it is common for people to ask for advice, suggestions and treatment. As a medical student, I have come across questions and situations that have alarmed me, however, I have never been overwhelmed. The story I heard on a flight from Lahore to Karachi particularly struck me. It concerned a woman's struggle to bear children, a seemingly ordinary ordeal, magnified by the fact that she was married to her first cousin.

I was sitting comfortably in an aisle seat when a man came by asking to exchange seats as he was sitting next to a lady who would prefer a woman.  Since it didn’t make much of a difference to me, I volunteered to to exchange seats with the man. This is how I ended up sitting beside Leena* who was married to her cousin.

We got to talking, and when she found out I was studying medicine she told me about herself. She was on her way to consult a geneticist at Aga Khan University Hospital. The trials and tribulations Leena* had while trying to conceive and give birth to a healthy baby brought tears to my eyes. She had suffered a miscarriage, two still-born babies, and poly-cystic ovarian disease, yet she was still hopeful that she'd be a mother soon.

To me, she was an example of courage and determination. After going through such a traumatic ordeal, the persistence exhibited by this lady struck me as nothing short of remarkable. It was fortunate that she had a supportive husband who would constantly reassure her that with the words:
"Every black cloud has a silver lining."

I wasn't sure what caused Leena and her husband's problems but her story inspired me. After landing in Karachi, I made it my personal mission to research inter-family marriages. I knew that there are numerous cases of inter-family marriages in Pakistan. With awareness cousin marriages have become highly stigmatized in the West, but in Pakistan and the Middle East I would estimate that up to 50 per cent of marriages  are between cousins or distant family members.

To this date, many are blissfully unaware of the complications that a couple can face when marrying within the family. There can be a myriad of genetic aberrations and chromosomal mutations that could result in sometimes fatal congenital anomalies. Children, for example, can be born with a hypoplastic heart, a condition where one side of the heart is severly underdeveloped, agenesis of a kidney, where one or both kidneys fail to develop and many more.

These mutations occur primarily because first cousin couples possess a higher than normal consanguinity; they have, on average an increased chance of sharing genes for recessive traits. A positive association between in-breeding and a very wide range of common adulthood disorders, including hypertension, coronary heart disease, stroke, cancer, uni/bipolar depression, asthma, gout, peptic ulcer, and osteoporosis has been reported. Therefore it is very important to make known the risks inter-family marriages pose and provide appropriate counselling to people in this relationship.

Here are a few things that can be done to protect children from being born with birth defects:

  • Comprehensive genetic education and premarital genetic counselling programs can help to lessen the burden of genetic diseases

  • Genetic education programs should be directed towards high school students

  • Preconception reproductive options should be explained to parents

  • All pregnant women should be given Folate,Vitamin B12 and Calcium to prevent neural tube defects, and serum levels of proteins (Alpha Feto Protein) should be monitored for Down Syndrome

  • New borns should be screened for hearing loss and inborn errors of metabolism

It is very important for our community to understand this message because many people are confronted with such problems.


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Nida Hasan A second year medical student at Dow Medical College.
The views expressed by the writer and the reader comments do not necassarily reflect the views and policies of the Express Tribune.


Ignorant Rationalist | 9 years ago | Reply First, even assuming that the deleterious phenotype arises solely from homozygosity at a single locus, the increased risk depends on the frequency of the allele involved; it is not an immediate consequence of the degree of relatedness between cousins. (Interestingly, despite the British biometricians' harsh criticism of Mendelism, they were the first to describe this dependency in 1911 [17,18].) If a deleterious recessive allele has a frequency q, the ratio of the recessive phenotype in the offspring of first cousins relative to a panmictic population is (1 + 15q)/16q, which means the increase in risk is greater for rarer conditions [19]. For example, if q is 0.01, the ratio is 7.2; if q is 0.001, it is 63.4. Consequently, statistics on the risks associated with cousin marriage are necessarily averages across many traits, and they are likely to be different for different populations, which will often vary in the frequency of particular deleterious alleles. In the Pakistani immigrant population, for example, the quoted high average rate of birth defects may mask a single trait (or small number of traits) at very high frequency, a situation with different medical consequences from one characterized by a larger number of less-frequent disorders. Second, children of cousin marriages are likely to manifest an increased frequency of birth defects showing polygenic inheritance and interacting with environmental variation. But as the NSGC report notes, calculating the increased frequency of such quantitative traits is not straightforward, and properly controlled studies are lacking. Moreover, socio-economic and other environmental influences will vary among populations, which can easily confound the effects of consanguinity. Inbred populations, including British Pakistanis, are often poor. The mother may be malnourished to begin with, and families may not seek or have access to good prenatal care, which may be unavailable in their native language [20]. Hence it is difficult to separate out genetic from socio-economic and other environmental factors. source: http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.0060320
Ignorant Rationalist | 9 years ago | Reply LoneLiberakPK: Your ignorance is mind boggling. "Pure hard science?" Here are the facts: There is no concrete scientific evidence that establishes causality between significantly increased risk of birth defects and cousin marriage. To say that it has been proven that cousin marriage is indeed deleterious is to live a hallucinating life, a life that deserves to not be lived. Paper: http://www.plosbiology.org/article/info:doi/10.1371/journal.pbio.0060320
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