Answer to Question #5016 Submitted to "Ask the Experts"
The following question was answered by an expert in the appropriate field:
I was found to have a Trisomy 18 pregnancy diagnosed by amniocentesis. I am 31 years old. I know that there are no specific reasons known why a Trisomy 18 occurs, but I wanted your opinion about whether radiation exposure through x rays of my finger during the time of conception and beyond could have contributed. I had a lead apron on for the x rays and fluoroscopic pictures. Because the diagnosis was confirmed by amniocentesis, I have terminated the pregnancy.
I am sorry about the outcome of your recent pregnancy. While you may feel that a Trisomy 18 is a rare event, it is not. The majority of spontaneous pregnancy losses are due to chromosome abnormalities. About 5,000 out of every million live births have a chromosome abnormality. Most chromosome abnormalities spontaneously abort and that may have happened to your pregnancy as well.
With regard to the cause of the Trisomy 18, I can tell you that the x-ray studies did not cause the trisomy. The abnormality is determined by abnormal sperm or egg development and occurs before or possibly at the time of fertilization. Even if there were an agent that could make trisomies, it could not accomplish the alteration after fertilization. These chromosome abnormalities are quite common and occur spontaneously as mistakes in cell division in developing eggs and sperm. You were just unlucky. Your risk and any potential mother's risk for a chromosome abnormality increases with age. If you have any other questions, please contact me. Good luck with your next pregnancy.
Robert Brent MD, PhD