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Inherited Disorders and Birth Defects

Engaged with the Cousin



I am 28 year old from Pakistan. I am engaged to my cousin. She is my Uncle`s (My mother`s brother) daughter. My uncle has heart problem (bypass). My father also felt some sort of pains in the recent past and doctor said after checkup that his heart vans are some how tight.

The elder sister of my fiancee is already wife of my elder brother. they lost two daughters (each before 3 months) due to the problem of heart. (hole in the heart tight vans). Now they have a 5 year son and he is suffering from the same problem (two holes in heart and heart size is also bigger than normal).

My grand mother had also heart problem.

it is worth mentioning that my younger sister is married to the Uncle`s son and they have one daughter with no such problem.

Now my family is insisting to marry with cousin and i am refusing due to cousin marriage issues. but they are not accepting my excuses. Should i marry to her? Please give me concrete advice.


The answer to your question really depends on what caused the heart defects in your family. From your description, it sounds like your brother’s children all were born with a complex congenital heart defect, while your sister has one child without problems.

Congenital heart defects (CHD) are the most common birth defect, affecting about 7 in 1,000 newborns worldwide. Between 20% and 45% of infants with CHD have other types of birth defects as well. Congenital heart defects can happen on their own, without any other problems or other family history, but about 10% are part of a genetic syndrome. There are more than 400 syndromes that have a congenital heart defect as part of it.

In general, consanguinity (related by blood) without knowing of any specific genetic disease in the family appears to cause some increase in the rate of birth defects and adds a risk of about 3 per cent. This risk is about double the general population risk for having a child with a birth defect or death in early childhood.

If there is a specific genetic disorder in the family, then it would depend on what the disorder is and its specific type of inheritance pattern – dominant, recessive, caused by a chromosome problem.

You do have an increased chance of having children with birth defects because you and your fiancée are first cousins, but how much chance I do not know. The best way to answer your question is for your family to find out what caused the heart problems in your brother’s children. If it is due to a genetic change, then you may be able to do genetic testing to see if you or your fiancée carries that gene. If that is not possible, you can talk to your doctor about what the chance is of having children with birth defects based on your specific family history. If there is a geneticist or genetics clinic near you - that would be the best place to do to get more information.

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Response by:

Anne   Matthews, RN, PhD Anne Matthews, RN, PhD
Associate Professor of Genetics
School of Medicine
Case Western Reserve University