Trisomy 18

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Trisomy 18

Trisomy 18 is a genetic defect related to the presence of an extra chromosome 18 caused by a problem that occurs when cells divide in the egg, sperm, or fertilized egg. The extra chromosome causes the fetus to develop abnormally with a number of physical and mental problems.

Trisomy 18 is also called Edward's syndrome. It is the second most common trisomy condition. (Down syndrome is the most common.) A fetus with trisomy 18 has three copies of chromosome 18.

Trisomy 18 can be identified during pregnancy. Doctors can do prenatal tests and fetal ultrasounds to screen for problems, and they can do chromosome tests to diagnose trisomy 18.

Most fetuses with trisomy 18 do not survive to birth, but some are born and live a couple of months to a couple of years. Babies born with trisomy 18 can have many physical problems, including heart and kidney problems, a small head with low-set ears, a chest with an unusual shape, and crossed legs. They also have severe mental retardation.

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Author	Sandy Jocoy, RN
Editor	Kathleen M. Ariss, MS
Associate Editor	Tracy Landauer
Associate Editor	Pat Truman, MATC
Primary Medical Reviewer	Sarah Marshall, MD - Family Medicine
Specialist Medical Reviewer	Siobhan M. Dolan, MD, MPH - Reproductive Genetics
Last Updated	May 20, 2008

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Last updated:	May 20, 2008
Author:	Sandy Jocoy, RN
Reviewed By:	Sarah Marshall, MD - Family Medicine, Siobhan M. Dolan, MD, MPH - Reproductive Genetics
Editors:	Kathleen M. Ariss, MS, Pat Truman, MATC

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