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Friday, May 24, 2013
Inherited Disorders and Birth Defects
Genetic balance translocated chromosomes
My wife and I have a healthy girl who is two and a half. We`ve been trying to have another with no luck. We`ve had three miscarriages. I have just foudn out that I have balanced translocation 13 and 14, the long arm on both. Would like to know what the odds are of having another healthy child.
The type of balanced translocation you have is called a Robertsonian translocation - where 2 acrocentric chromosomes (chromosomes # 13, 14, 15, 21 and 22) have lost the tiny short arms of the chromosome and the two longer arms have fused.
The most common Robertsonian translocations are between chromosomes #13 and 14, and #14 and 21. In a review of the literature, the 13q14q balanced translocation you have is the most common. It has been estimated that about 1 in 1300 people have this type of Robertsonian translocation.
As you may already know, the chance of having an egg that has the unbalanced translocation vs. the normal or balanced rearrangement depends on how the chromosomes line up, divide and separate. In theory, there is a 25% chance that the gametes (eggs or sperm) that the mom or dad produces - will have a normal chromosome complement, a 25% chance that the egg or sperm will have the balanced translocation (like the parent) and a 50% chance that the egg or sperm would produce an unbalanced chromosome complement.
Almost always the eggs or sperm that produce an unbalanced complement are miscarried because they are not viable - not able to produce a live born child. So the chance for you to have another healthy child who has a normal chromosome complement or who is a carrier like you are - is excellent. The major concern would be for another miscarriage. Unfortunately, researchers do not know why some people who are carriers of balanced chromosome rearrangements miscarry more frequently than other people with the same chromosomal rearrangement.
If you have not already done so, I would highly recommend that you speak to a genetic counselor or geneticist to discuss this in detail and what it means regarding your future children. You can locate a genetics center near you at the National Society of Genetic Counselors' resource website listed below.
Anne Matthews, RN, PhD
Associate Professor of Genetics
School of Medicine
Case Western Reserve University