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Inherited Disorders and Birth Defects

Do I have to avoid pregnancy in cousin marriage?

08/31/2007

Question:

I am 26 yrs old girl and a patient of J.M.E. and taking epival+rivotril as medicines. In our family there is concept of cousin marriages,my parents are also first cousin. My younger brother was mentally and physically retarded, me and my brother are normal. My brother had two misscarriages. Now I want to ask that if I will marry my first cousin than are there any possibilities of birth defects in our children?

Answer:

JME is an inherited disorder and researchers have found at least 6 genes that can cause JME. Most researchers believe it is an autosomal dominant condition, that is, anyone with a gene that codes for JME has a 50-50 chance of passing that gene on to their children. Also, some people who inherit a JME gene or genes do not show JME. This is called incomplete penetrance. However, their children may inherit the JME genes and will have the disease. This sometimes looks like the disease seems to skip generations.

In your case, you seem to have one or more genes that cause JME so you have a 50-50 chance of passing those genes on to any of your children and they may have JME as well. If you marry your first cousin, he may also carry a gene or genes that cause JME, but he does not show signs of it. If he does, then there is a chance that he could pass that gene on to your children as well.

Your younger brother’s mental and physical retardation as well as your other brother’s miscarriages are most likely not related to JME but to something else. In any case, when you marry a relative, because you share more genes in common than if you married someone who was not related to you, there is an increased chance that your children could inherit a genetic condition or birth defect.

I would recommend that you talk to a genetic counselor or geneticist because this is a complicated situation. You can locate a genetics center near you at the National Society of Genetic Counselor Resource Center. The website is below.

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