- 18 trisomy
- Chromosome 18 duplication
- Chromosome 18 trisomy
- Edwards syndrome
- Trisomy 16-18 (formerly)
Your QuestionI lost a baby to Edwards syndrome. Are my surviving children at risk for any problems as a result?
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Questions on this page
About 5% of people with trisomy 18 have 'mosaic trisomy 18' (when there is an extra copy of the chromosome in only some of the body's cells). The severity of mosaic trisomy 18 depends on the number and locations of cells with the extra copy.
Very rarely, an extra piece of chromosome 18 is attached to another chromosome; this is called translocation trisomy 18, or partial trisomy 18. If only part of the long (q) arm of chromosome 18 is present in 3 copies, the features may be less severe than in people with full trisomy 18.
Mosaic trisomy 18 (when some body cells have trisomy 18 and some have a normal chromosome make-up), is also typically not inherited. Mosaic trisomy 18 is also due to an error in cell division, but the error occurs early in embryonic development. About 5% of affected people have a mosaic form of trisomy 18.
Partial trisomy 18 (when only part of chromosome 18 is present in 3 copies) can be inherited. An unaffected parent can carry a rearrangement of genetic material between chromosome 18 and another chromosome. This rearrangement is called a balanced translocation because there is no extra or missing genetic material. However, a person with a balanced translocation has an increased risk with each pregnancy to have a child with trisomy 18.
Most cases of trisomy 18 occur as random events during the formation of reproductive cells (eggs and sperm). The risk of recurrence of trisomy (21, 13 or 18) in families of an individual with trisomy 18 is around 1%. However, in families in which trisomy 18 is caused by a translocation, the recurrence risk is higher if one of the parents is a carrier of a balanced translocation. Parents who have a child with translocational trisomy 18 and want additional children are encouraged to have chromosome studies due to this increased risk. The risk to siblings of individuals with trisomy 18 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
* 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.
- Trisomy 18. Genetics Home Reference. March, 2013; http://ghr.nlm.nih.gov/condition/trisomy-18. Accessed 8/23/2015.
- Haldeman-Englert C. Trisomy 18. MedlinePlus. August 2011; http://www.nlm.nih.gov/medlineplus/ency/article/001661.htm. Accessed 1/17/2012.
- Trisomy 18. Genetics Home Reference (GHR). January 2009; http://ghr.nlm.nih.gov/condition/trisomy-18. Accessed 1/17/2012.
- A. Verloes . Trisomy 18. Orphanet. May 2008; http://www.orpha.net/consor/cgi-bin/OC_Exp.php?lng=EN&Expert=3380. Accessed 12/16/2008.