Jack Hartsell 2A

Interesting Facts

  • Trisomy 18 (also known as Edward syndrome) is a chromosomal condition in which all or a part of chromosome 18 is present in the cells of the body three times (trisomy) rather than the usual two times
  • Appears to affect females three to four times more frequently than males
  • About 1% of all recognized miscarriages occur in association with trisomy 18
  • There are two main types of Trisomy 18 - 1) Classic Trisomy 18, the presence of three copies of chromosome 18 in all cells. 2) Mosaic Trisomy 18, the presence of three copies of chromosome 18 in only some cells. About 10 percent of people with Trisomy 18 have a mosaic form.

Genetic Transmission

  • The chromosomal problem in trisomy 18 is due to an egg cell or, rarely, a sperm cell that is formed containing one copy of each chromosome and an extra copy of chromosome 18, ie. 24 chromosomes rather than 23. When that egg combines with sperm containing the usual 23 chromosomes, the baby conceived has 47 chromosomes in the cell of their body rather than the usual 46
  • The chance for having a child with trisomy 18 increases with the mother’s age
  • If a woman has had a child with trisomy 18 there may be a small additional increase in risk over her age risk for having another child with the condition
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Symptoms, Diagnosis and Frequency

  • The syndrome impacts severely upon intellectual and physical development
  • Occurs in about 1 in 5,000 to 1 in 7,000 live births
  • Screening and diagnostic testing (where indicated) for trisomy 18 is available in pregnancy
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Life Expectancy and Treatment

  • Of all babies born with the extra copy of chromosome 18, 50% do not survive one week of age and 90% do not survive past the first year of life
  • Treatment limited to improving quality of life and understanding symptoms


Centre for Genetics Education -