What Is Down Syndrome?

Down syndrome is a chromosomal anomaly resulting in an additional full or partial copy of chromosome 21. Approximately 1 in 800 babies is born with Down syndrome and around 70% are born to mothers under 35. Down syndrome was named after Dr. Langdon Down who was the first person to describe the syndrome. There are no known factors to explain the difference in cell development which results in 47 chromosomes rather than the usual 46. It happens at conception and the occurrence of Down syndrome has not been linked to any activities before or during pregnancy. Roughly equal numbers of males and females with Down syndrome are born to mothers of all ages, ethnic groups, countries and economic backgrounds.

Being blueprints for the body's development, genes and chromosomes play a large part in determining a person's characteristics. As many as 120 features have been associated with Down syndrome, although many individuals have no more than 6 or 7 of these. Characteristics can include physical features such as a flat facial profile and upward slanting eyes, intellectual impairment of varying degrees and increased chances of certain medical conditions including congenital heart defects, hearing loss and vision difficulties.

More information:

About Down Syndrome - Factsheet