Typically, people have two copies of chromosome 21 in every cell in their body. People with Down syndrome have three copies of chromosome 21 in every cell. Having too much genetic material (chromosomes) leads to health and learning difficulties. Since the extra chromosome is found in every cell in the body, it can not be removed.
People with Down syndrome usually have mild to moderate intellectual delay. Individuals with Down syndrome learn over their lifetime however, the rate at which they learn will be slower than an average individual. Their learning will continue to be behind people their own age for their entire life.People with Down syndrome are more likely to have health problems than the average person like heart, stomach, bowel, thyroid, vision and hearing difficulties. Treatment is available for many of these health conditions.
People with Down syndrome generally live into their fifties.Each person with Down syndrome is different. There is no way to test how serious the disabilities will be.
In general, about one in 1000 births has Down syndrome. The chance of having a child with Down syndrome increases with the mother’s age.