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Inherited Disorders and Birth Defects

I`m a pregnant balanced translocation carrier

07/09/2008

Question:

I have had 4 miscarriages and my karyotyping shows a balanced reciprocal translocation. It is t(1;3) (q32.3;q26.1). I understand that this involves a significant chunk of two major chromosomes. Based on my history, I would assume an embryo missing either part from 1 or 3 would not be viable. Should I have CVS or amniocentesis done? I just don`t know if I could make the decision to abort if the results showed a missing chunk. I have already seen a genetic counselor, but still don`t know what to do.

Answer:

As you probably know, because you have a balanced reciprocal chromosomal translocation, you have 1) a chance to have a child who has normal chromosomes (no translocation); 2) a chance to have a child who is a balanced translocation carrier just like you and we would expect to have no problems due to the translocation; and 3) a chance to have a pregnancy where there is too much or not enough chromosomal material (in your case, having too much or not enough of chromosome 1 and too much or not enough chromosome 3). These pregnancies almost always miscarry - most likely the reason for your other miscarriages.

In the current pregnancy, the only way to know what the baby's chromosomes are is to do some type of diagnostic test - a CVS (usually done between 10 and 12 weeks gestation) or an amniocentesis (usually done between 15-22 weeks). If an abnormality is found, the decision to either continue the pregnancy or terminate is a very personal one - one that only you and your family can make. Many couples choose to have diagnostic testing, not to consider terminating a pregnancy, but so that they have a "heads up" of what to expect when the baby is born. Others would prefer not to know ahead of time and just "wait and see". However, almost all couples have the same kinds of thoughts and concerns that you have and "just don't know what to do" until they do it.

As most pregnancies that have unbalanced chromosome rearrangements are more likely to miscarry during the first trimester, you might consider waiting to see if you miscarry. If you do not miscarry, but are still very concerned, then you could consider having the amniocentesis done to check the baby's chromosomes. Again, these are very personal decisions that only you and your family can make based on your beliefs and values. Sometimes talking to your doctor or your clergy is helpful. If you have already talked to the genetic counselor, I am sure he or she would be happy to talk to you again to rediscuss your concerns. There are no right or wrong answers - whatever you decide it will be the right decision for you and your family.

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Response by:

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