Trisomy 18, also known as Edward's Syndrome, is a genetic disorder caused by the presence of an extra copy of chromosome 18. It is three times more common in girls than boys and can cause physical abnormalities like clenched hands, crossed legs, and heart defects. Treatment is tailored to each individual child but the outcome is often poor as many children with Trisomy 18 die within the first year. Genetic testing during pregnancy can identify risks and help parents plan for care of an affected child.