Down syndrome is a genetic condition caused by trisomy of chromosome 21. It occurs in about 1 in 660 births. Key features in newborns include slanted eyes, small ears, loose skin on the back of the neck, and poor muscle tone. Individuals with Down syndrome often have health issues such as heart defects, hearing or vision problems, gastrointestinal abnormalities, thyroid disorders, and psychiatric conditions. Lifelong healthcare involves screening and management of associated medical problems with a focus on development, education, independence, and quality of life.