Trisomy 16: the Leading Cause of Miscarriage

Up to 25 percent of all pregnancies will end in miscarriage during the first trimester. If you are over the age of forty then the risk of miscarriage increases to 35 percent. The leading cause of these miscarriages is normally a chromosomal abnormality known as Trisomy 16. This Aneuploidy is the leading cause of fetal death in over 50 percent of miscarriages. Full Trisomy 16 means that the fetus has three sets of the chromosome 16 which is incompatible with life. These pregnancies will always lead to miscarriage.

The majority of Trisomy 16 pregnancies will terminate prior to six weeks. At six weeks the fetus's heart will begin to be detectable on an ultra sound. Normally, a Trisomy 16 fetus will never have a fully functioning heart so it will fail to beat. The fetus normally perishes in utero at 5 weeks which will result in a miscarriage.

If you suffer one miscarriage then your chances increase that the next pregnancy will result in miscarriage as well. The statistics are lower that you will have a second miscarriage if you are below the age of thirty five but if you are over the age of thirty five then the chances of miscarriage increase dramatically with each passing year.

Trisomy 16 can occur in any pregnancy but it is more common with mothers of advanced maternal age. It is caused from either the egg or the sperm containing an extra copy of chromosome 16. As women age their eggs age as well. Some studies believe that after the age of 40 seventy five percent of the eggs a woman ovulates contain aneuploidy. Estimates say that a woman who is age 40 has a one in sixty three chance of delivering a baby with a Trisomy such as Trisomy 21. This statistic is only for a woman who delivers a live child. It does not take into account the number of miscarriages that are suffered due to Trisomy 16 or a wide variety of other Trisomies. Trisomy can occur in any chromosome of the human body. But the most common are Trisomy 21,16,18, and 13. Studies strongly suggest that over 50 percent of all embryos conceived by a woman over the age of 40 will have a chromosomal abnormality. The vast majority of these will never implant in the uterus or be miscarried in early pregnancy. Some women will never even know that they were pregnant if the egg does not implant or the miscarriage takes place within days of a missed period.

No one likes to face the fact that they are getting older but the sad reality is that many women wait to have children nowadays due to careers or other factors and this results in the loss of the fertility window. Not only do women over the age of forty face decreased fertility but they also face the cold hard facts of chromosomal defects that are age related and often result in miscarriage or the live birth of a disabled child.

If you suffer from more then one miscarriage many doctors will collect tissue samples either from a natural miscarriage or a DandC from a partial miscarriage to analyze the cells. They will be able to confirm a diagnosis of Trisomy from these cell samples. Remember, that a Trisomy can occur in any of the chromosomes but it is normally Trisomy 16 that is the most widely affected in humans who suffer miscarriage. If you have a diagnosis of Trisomy 16 or any other Trisomy as the cause of miscarriage then you will need to meet with a genetic counselor to discuss the chances of ongoing maternal Trisomy problems. Remember that some Trisomies result in live births but the child is handicapped so if you want to continue trying to conceive you may be faced with one of the other Trisomies which will make your decisions harder because you will be faced with either keeping the child or terminating the pregnancy. Ask yourself if you and your partner are prepared to do this because you will never be the same once it is all over.

A history of miscarriage due to Trisomy 16 reflects that we are aging and, perhaps, its time to consider how many more times you will try to conceive a healthy child only to lose all your hopes and dreams to miscarriage or be faced with a life and death decision that none of us want to make.

Sources:

http://www.medgen.ubc.ca/robinsonlab/mosaic/specific/trisomy16.htm

http://www.americanpregnancy.org/pregnancycomplications/miscarriage.html

http://www.reproductivegenetics.com/aneuploidy.html

http://www.mfm-evms.org/recurrent.html