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Sunday, April 19, 2015
Inherited Disorders and Birth Defects
Balanced Translocation t(1,3)
We recently found out through amniocentesis that our child has a balanced translocation between chromosomes 1 and 3. The ultrasounds so far show that the baby is growing normally and everything appears normal. We just found out that neither my wife nor I have a translocation of any type. What kind of problems are we possibly looking at for our child? What are the possibilities of these problems actually occurring? Any information would be helpful. Thanks
A balanced translocation occurs when two pieces of chromosomes break off and switch places with each other. If all the chromosomal material is present, just rearranged – that is, switched places (translocated) - this person should have no health problems since all the chromosomal material needed is present and functioning properly. This is called a balanced translocation.
However, there can be problems if some of the chromosomal material that was switched is lost or duplicated when the chromosomes broke and the switch took place – then there is extra and / or missing information that can lead to birth defects and cognitive problems such as mental retardation. This is an unbalanced translocation.
When a translocation occurs for the first time and it not inherited from a parent, it is called a de novo translocation. In the majority of cases, the translocation is truly balanced and there is a normal outcome. However, as there is no parent with the same translocation to compare it to, it is impossible to say that there will be no problems. Depending on the specific areas of the chromosomes that were translocated and what specific genes are located at these sites - there is a very small possibility that some genes in the area were disrupted or that genetic material was lost or added that is too small to detect.
By far, most babies diagnosed with a de novo translocation after amniocentesis are born without any problems. Experts in the field suggest that there may be about a 3% increased chance above the background chance for all pregnancies to have a baby born with a birth defect or cognitive problems. The background risk for birth defects for everyone is about 3 %. The fact that the baby is growing normally and there are no problems noted so far on ultrasound is reassuring.
If you have not already done so, I would suggest that you speak to the genetic counselor or a geneticist to discuss the specific chromosomal translocation that was found in the baby. They would be able to provide you with more detailed information. You can locate a genetics center near you at the National Society of Genetic Counselors’ Resource center at the website below.
Anne Matthews, RN, PhD
Associate Professor of Genetics
School of Medicine
Case Western Reserve University