What is Edwards syndrome? (Back to Top)

Edwards syndrome, also called trisomy 18, is a genetic disorder associated with the presence of extra material from chromosome 18. The extra material interferes with normal development.^[1] This condition is associated with low birth weight; a small, abnormally shaped head; a small jaw; a small mouth; and clenched fists with overlapping fingers. Infants born with Edwards syndrome have mental retardation, heart defects, and organ abnormalities affecting most systems of the body.^[2] Fifty percent of infants with this condition do not survive beyond the first week of life. Some children have survived to teenage years, but with serious medical and developmental problems.^[1] Approximately 80 percent of newborns affected by this disorder are female.^[2]

What causes Edwards syndrome? (Back to Top)

People with Edwards syndrome have additional DNA from chromosome 18 in some or all of their cells. The extra material disrupts the normal course of development, causing the characteristic features of Edwards syndrome.^[2]

Edwards syndrome results when each cell in the body has three copies of chromosome 18 instead of the usual two copies. A small percentage of cases occur when only some of the body's cells have an extra copy of chromosome 18, resulting in a mixed population of cells with a differing number of chromosomes. Such cases are sometimes called mosaic trisomy 18.^[2]

Very rarely, a piece of chromosome 18 becomes attached to another chromosome (translocated) before or after conception. Affected people have two copies of chromosome 18, plus extra material from chromosome 18 attached to another chromosome. With a translocation, the person has a partial trisomy for chromosome 18 and often the physical signs of the syndrome differ from those typically seen in Edwards syndrome.^[2]

The risk of having a child with trisomy 18 increases as a woman gets older.^[2]

Can Edwards syndrome be inherited? (Back to Top)

Are my children at risk for any problems as a result of our family history of Edwards syndrome? (Back to Top)

Most cases of Edwards syndrome occur as random events during the formation of reproductive cells (eggs and sperm).^[2] The risk of recurrence of trisomy (21, 13 or 18) in families of an index case with Edwards syndrome is around 1%. However, in families in which Edwards syndrome is caused by translocation, the recurrence risk is higher if one of the parents is a carrier of a balanced translocation.^[3] Parents who have a child with translocational trisomy 18 and want additional children are encouraged to have chromosome studies due to this increased risk.^[1] The risk to siblings of individuals with Edwards syndrome depends, in large part, on the genetic status of the parents, as translocation cases can be passed through families with carriers being asymptomatic. Genetic studies (chromosome analysis) can determine if translocations are present. 

We recommend that you discuss this information and your concerns with a genetics professional. The following online resources can help you find a genetics professional in your community:

 * GeneClinics - A searchable directory of US and international genetics and prenatal diagnosis clinics. To locate genetics clinics in the United States, go to the following link and click on 'Clinic Directory' to find a genetic service close to you. 

  * ResourceLink - A database of genetics counseling services, searchable by location, name, institution, type of practice, or specialty. Hosted by the National Society of Genetic Counselors.