Edwards syndrome, also called trisomy 18, is a genetic disorder associated with the presence of an extra chromosome 18. It is the second most common autosomal trisomy among liveborn children.

FREQUENCY OFOCCURRENCESeen 1 in 6000 live births
• About 1 in 3000 conceptions is diagnosed as having an extra copy of chromosome 18, but most fetuses with trisomy 18 die during pregnancy.
INHERITANCESporadic / not inherited
• Most cases of Edwards syndrome (primary trisomies) are not inherited including mosaicism.
• Trisomy 18 due to a translocation can be inherited. A carrier can have a rearrangement of genetic material between chr 18 and another chromosome. This is called a balanced translocation, because there is no extra material from chr 18. Although they do not have signs of the syndrome, people who carry this type of balanced translocation are at an increased risk of having children with the condition.
Limited lifespan, median survival of 4 days
• Survival rates:
– 40% chance of surviving to 1 month
– 5% chance of surviving to 1 year
– 1% chance of surviving to 10 years
CAUSEA third chromosome 18 appearing in all or some of the cells
• Primary trisomy: the presence of an entire third chr 18 in all cells.
• Unbalanced translocation: an extra portion of chr 18 attached to another chromosome,which may be due to a balanced translocation of one parent.
• Mosaicism: some normal cells with 46 chromosomes, others with extra chr 13.
  • Low birth weight
  • Neonatal hypotonia followed by hypertonia
  • Growth delay
  • Small head (microcephaly)
  • Long head (dolichocephaly)
  • Craniofacial abnormalities
  • Eye malformations (microphthalmia, coloboma)
  • Skeletal abnormalities (clenched fist, thumb aplasia, malformed feet)
  • Incomplete development of lungs (pulmonary hypoplasia)
  • Congenital heart defects
  • Gastrointestinal abnormalities
  • Urogenital malformations
  • Neurological problems (anencephaly, hydrocephaly and other brain malformations)
  • Severe learning disability

People with Edwards syndrome can have a range of severe medical problems. For the most part of their lives they require specialised nursing in a hospital or hospice.

The majority of non-mosaic patients develop only limited autonomy (absence of speech and ambulation).

For unknown reasons, the rate of survival is higher in females than in males, leading to a female predominance among live-born trisomy 18 infants.

Medical management of patients with trisomy 18 is planned on a case-by-case basis and depends on their individual circumstances of the patient. Treatment is usually supportive only.

Surgical treatment of the malformations does little to improve the poor prognosis associated with this syndrome: more than 90% of infants die within the first year of life from cardiac, renal or neurological complications, or from repeated infections. Prolonged survival (in some cases into adulthood) mainly happens in cases involving mosaic or partial trisomy.