Font Size

Trisomy 18 (Edwards Syndrome)

Trisomy 18 Facts

  • Trisomy 18 (Edwards syndrome) results from the presence of an extra copy of chromosome 18.
  • Trisomy 18 leads to severe intellectual and physical defects.
  • The prognosis of trisomy 18 is poor. Half of those affected do not live beyond the first week of life and a low percentage of infants with this condition live beyond the first year.
  • Common features of trisomy 18 include a low birth weight; a small jaw and mouth; an abnormally shaped, small head; overlapping fingers and clenched fists; and defects in the heart and other organs.
  • Trisomy 18 occurs on average in 1 out of every 5,000 births.
  • Most fetuses with trisomy 18 die in the prenatal period (prior to delivery).
  • Girls are affected more commonly than boys.

What is Trisomy 18?

Trisomy 18, also known as Edwards Syndrome, is a severe genetic disorder associated with intellectual disability and abnormalities in many organs. Trisomy 18 was first described in 1960 and results from an additional copy of chromosome 18 (normal cells carry two copies of each chromosome; the term, "trisomy," refers to the presence of three of a given chromosome). Only about 10% of affected infants survive past one year of age, and half of affected infants do not live beyond the first week of life.

Medically Reviewed by a Doctor on 12/28/2015

Must Read Articles Related to Trisomy 18 (Edwards Syndrome)

Pregnancy (First, Second, Third Trimester)
Pregnancy Week by Week Pregnancy occurs when an egg is fertilized by a sperm, grows inside a woman's uterus (womb), and develops into a baby. In humans, this process takes about 280 d...learn more >>

Patient Comments & Reviews

The eMedicineHealth doctors ask about Trisomy 18 (Edwards Syndrome):

Trisomy 18 - Symptoms

What were the symptoms of your baby with Trisomy 18?

Definition of Trisomy 18

Trisomy 18 syndrome: There are three instead of the normal two chromosomes #18. Children with this condition have multiple malformations and mental retardation due to the extra chromosome #18. The children characteristically have low birth weight, small head (microcephaly), small jaw (micrognathia), malformations of the heart and kidneys, clenched fists with abnormal finger positioning, and malformed feet. The mental retardation is profound with the IQ too low to even test. Nineteen out of 20 (95%) of these children die before their first birthday. The condition is also called Edwards syndrome in honor of the British physician and geneticist John Edwards who discovered the extra chromosome in 1960.

SOURCE: Trisomy 18 Syndrome.

Medical Dictionary