You are in Medical Library . 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.
There may be many other abnormalities noted. At the birth of the child, an unusually small placenta may be noted. Chromosome studies show trisomy 18, partial trisomy, or translocation . Treatment Treatment is supportive, but life-sustaining measures are not recommended. The abnormalities of trisomy 18 are generally not compatible with more than a few months of life.