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Inherited Disorders and Birth Defects

Miscarriage due to unbalanced translocation

06/11/2008

Question:

I have had 2 miscarriages. A miscarriage in 2006, a healthy boy born in 2007, and a miscarriage in 2008. After the 2nd miscarriage we opted for chromosome testing on the baby. It was determined that the bady had a 10-14 unbalanced chromosome translocation. So we understand why this baby did not make it.

My husband and I are currently waiting for our results for our chromosome testing. So we can see if the baby`s translocation was due to one of us having a balanced translocation, or if the baby`s translocation was completely random.

My question is, what are the chances that my husband or myself have a translocation vs. it being completely random? Are there statistics showing how often a unbalanced translocation occurs from parents without a balanced translocation vs. how often an unbalanced translocation occurs from a parent with a balanced transloction?

Thank you.

Answer:

It is estimated that about 1 person in 673 to 1 in 1000 of the general population carries a balanced reciprocal translocation. This data comes from prenatal and newborn studies. A reciprocal translocation happens when two different chromosomes break and exchange pieces with each other. As long as all of the chromosome material is present - nothing missing or added - there should be no health problems caused by the translocation.

Most unbalanced translocations are not inherited (this is called a de novo unbalanced translocation), that is, neither parent has a balanced translocation. However, it is estimated that in about 4% of couples who have had more than 2 or 3 miscarriages, one of the parents will have a balanced translocation.

These are important questions. You probably have, but if you have not already spoken to a genetic counselor or geneticist, I would highly recommend that you do. You can locate a genetics center near you at the National Society of Genetic Counselors website listed 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