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Inherited Disorders and Birth Defects

Birth Defects Due to Cousin Marriage

06/23/2009

Question:

I have come to know that many prob regarding birth defects can take place if one gets married with a first cousin. I`m going to get married with my first cousin. My mother and my cousin`s mother are real sisters, but our fathers are not relatives. I want to know whther there are any particular kind of medical tests with which we can ascertain that can we have this problem or not? Please tell me because in my family it`s not possible to visit the doctor, just to have knowledge. But if there are tests, I`ll surely ask my parents to do it first.

Answer:

The answer to your question really depends on your family history and whether or not there are any genetic disorders or birth defects in your families.  In order to do any testing, you need to know what genetic diseases to look for. 

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.  First cousins have a higher chance of sharing the same genes - and since most people carry at least a couple of recessive genes that could lead to a genetic disorder, children from a first cousin mating would be at some increased risk.

Again, you would need to have some idea of what to look for if you were to have genetic testing.  While there hundreds of genetic tests that could be done, it would not be possible to do them all (and extremely expensive). 

I would recommend that you talk to your mothers about what diseases run in your families.  If there are some, then I would recommend that you talk to a genetic counselor or geneticist to review your family histories in detail.  Then you would have specific information.  You can ask to your doctor for a referral or contact the National Society of Genetic Counselors at the website below to find a genetics center near you.

Related Resources:

National Society of Genetic Counselors Resource Center

For more information:

Go to the Inherited Disorders and Birth Defects health topic, where you can:

Response by:

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