The Complex and Profound Effects of Trisomy 13


Can you explain what the trisomy 13 genetic defect is?

Dr. Greene's Answer

The 13th chromosome contains blueprints that direct a baby’s development in the early weeks following conception. When a child has an extra 13th chromosome, as is the case in trisomy 13, the genetic messages are confused and contradictory – there’s just too much to juggle. This results in multiple significant defects in major organ systems. The brain is often the most severely affected. Most children with trisomy13 have some kind of heart defect. It’s also not unusual for these children to be born blind, deaf, and with no sense of smell. Taste and touch become the limited means by which a mother can convey an ocean of feeling.

Trisomy 13 was first described in 1657, but three hundred fifty years of medical knowledge have not improved the outlook for children born with this syndrome. Most babies who are conceived with trisomy 13 die early in gestation. Of the babies who live to be born, the median age of survival is to 7 days of life. Only 9 percent reach their first birthdays — and these have severe mental defects and seizures (Smith’s Recognizable Patterns of Human Malformation, Saunders 2006). The farthest we’ve advanced is in the development of early detection. Trisomy 13 is often detectable on ultrasound as early as 11-14 weeks. Chorionic villous sampling can detect trisomy 13 by 12 weeks. Amniocentesis, usually performed after 16 weeks gestation, can give a definite answer if any question still remains.

Often trisomy 13 is associated with older mothers. Even so, the risk of having another baby with trisomy13 is usually very low, unless the trisomy 13 is a translocation. A translocation is not associated with mom’s age, but is a hereditary chromosome problem. The risk of recurrence in some types of (balanced) translocations can be quite high. The inheritance of trisomy 13 is very complex.

July 1, 2011
Published on: June 09, 1997
About the Author
Photo of Alan Greene MD
Dr. Greene is a practicing physician, author, national and international TEDx speaker, and global health advocate. He is a graduate of Princeton University and University of California San Francisco.
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Recent Comments

I had a baby with trisomy 13. I carried him full term and he lived for 24 hours. He carried a 13/14 roberstonian translocation. We were told that our chances of this reoccurring would be 1% if we were carriers of this translocation in ourselves. We decided not to proceed with the genetic testing on ourselves only because we thought that if the information were not to change then we thought even if we carried the translocation we still had very good odds of having a healthy baby.

We have 3 healthy children, but have had 4 losses including the most recent which was at 13 weeks. We had an early amnio done because we saw some problems via ultrasound and the the amnio confirmed the same 13/14 translocation. Now, we were told that with this translocation and being carriers we would still only face a 1% chance of reoccurrence. But, here we are struck by lightning twice or are the statistics wrong and we actually have a much higher trisomy 13 rate?

Thank you so much for you time and your help.