Trisomy 18

Alternative names:

Edwards syndrome

Definition:

A syndrome associated with the presence of a third (extra) number 18 chromosome.

Causes, incidence, and risk factors:

Trisomy 18 is a relatively common syndrome affecting approximately 1 out of 8,000 live births and affecting girls more than twice as often as boys. Multiple abnormalities are associated with the presence of an extra number 18 chromosome, many which are not compatible with more than a few months of life. Few infants survive beyond the first year.

Common findings include low birth weight, mental retardation, low-set ears, malformed ears, small jaw (micrognathia), hand abnormalities, congenital heart disease, hernias, and cryptorchidism. There may be many other abnormalities noted.