Trisomy 18 (Edwards' syndrome) is a rare genetic disorder in which chromosome 18 is present three times instead of twice. It usually occurs spontaneously and is not hereditary.

Children with trisomy 18 often have a very low birth weight, a small head, characteristic facial features, malformations of the hands, feet and internal organs as well as severe developmental delays. Many of those affected also suffer from heart defects, breathing problems and seizures.

The prognosis is usually serious, with many children dying in the first few months of life. Nevertheless, there are also cases in which children with trisomy 18 live longer and require intensive medical and nursing support.