About Down Syndrome

Down syndrome is a condition in which a person is born with an extra copy of chromosome 21.  The condition is associated with intellectual disability, a characteristic facial appearance, and weak muscle tone (hypotonia) in infancy.  People with Down syndrome may have a variety of birth defects. About half of all affected children are born with a heart defect.  Individuals with Down syndrome have an increased risk of developing several medical conditions, including hearing and vision problems, gastroesophageal reflux, and celiac disease.  About half of adults with Down syndrome develop Alzheimer’s disease.  Women who are 35 years or older when they become pregnant are more likely to have a pregnancy affected by Down syndrome than women who become pregnant at a younger age.  However, most babies born with Down syndrome are born to mothers less than 35 years old, because there are many more births among younger women.

Down syndrome is the most common genetic cause of intellectual disability, the most common autosomal trisomy, and one of the most visible and universally recognized genetic syndromes. Each year there are approximately 6,000 babies born in the United States with Down syndrome, affecting approximately 1 out of every 700 babies. However, with appropriate support and treatment, many people with Down syndrome lead happy, productive lives. Within the past 25 years, the average lifespan for a person with Down syndrome has doubled, from 30 to 60 years.  Despite this increase in lifespan, individuals with Down syndrome and their families face significant and changing health challenges.

This page last reviewed on June 20, 2018