Wednesday, October 22, 2014
Inherited Disorders and Birth Defects
Could he have a balanced translocation?
In the past 2 years I`ve had 2 second trimester missed miscarriages, both discovered at exactly 18 weeks. It was found both times that the fetus had died between 16-17 weeks. My first three pregnancies with my ex husband were normal, full term and resulted in 3 healthy babies. I`ve since remarried and both pregnancies with my current husband who has no children have resulted in these miscarriages. What are the chances he has a balanced translocation and this is causing us to lose these babies? Also, what kind of translocations typically cause this and why did the pregnancy progress to 16 weeks and just stop? I had an u/s @ 14 weeks before that showed a strong heartbeat and also had the Down Syndrome testing that came back I was not at high risk. If he has this what chances do we have of having a healthy baby?
There could be a number of reasons for having 2 miscarriages. First, it may be just chance. About 15% to 20% of all pregnancies end in miscarriage and we do not know for sure what caused it. Second, chromosomal problems (having too much or not enough chromosome material) usually cause miscarriages. Other factors that can cause miscarriages include hormone or immunology problems, infections, abnormalities of the uterus or a weakened cervix, and some health problems of the mom - such as diabetes that is not very well controlled, thyroid disease and lupus (systemic lupus erythematosus).
If there is a chromosomal translocation - there is an increased chance to have miscarriages. A person who has a balanced translocation is someone who has had two pieces of chromosomes break off and switch places with each other. In this case, as all the chromosome material is present but rearranged (translocated) - this person should have no health problems since all of the chromosome material needed is present and functioning properly. There is no way to tell whether or not a person has one of these rearrangements unless you look at his or her blood to examine the chromosomes.
However, eggs and sperm can produce pregnancies with an unbalanced translocation - chromosome material is lost or duplicated. Usually the eggs or sperm that produce an unbalanced chromosome rearrangement are miscarried. So most of the time, a woman or a man who is a carrier of a balanced chromosomal translocation will have children with normal chromosomes or will miscarry. In couples who have had recurrent miscarriages, about 4% of the time one partner of the couple will have a balanced translocation.
While most pregnancies that have chromosome problems miscarry in the first trimester, occasionally they can miscarry later or there can be a live born child. The Down syndrome test you mention is a screening test which can give you a risk figure - what is the chance that the pregnancy may have a problem, but it does not diagnose the problem.
You ask excellent questions that are complicated. I would highly recommend that you talk to your doctor about finding out what may have caused your pregnancy losses. Additionally, you may want to talk to a geneticist or genetic counselor about these issues. You can locate a genetics center near you through the National Society of Genetic Counselors' Resource center website below.
Anne Matthews, RN, PhD
Associate Professor of Genetics
School of Medicine
Case Western Reserve University