Down syndrome, also known as Trisomy 21, occurs in most cases at the point of conception when a baby is conceived with an extra copy of chromosome 21. This additional genetic material alters the course of development and causes the characteristics associated with Down syndrome.

Down syndrome is not caused by anything that parents might or might not do and the condition affects approximately one in every 1150 births in Australia.

The incidence of births of children with Down syndrome increases with the age of the mother. However, due to higher fertility rates in younger women, about four in five children with Down syndrome are born to women under 35 years of age

Down syndrome is one of the most common single identified cause of intellectual disability. The severity of the effects on physical and intellectual functioning varies greatly among individuals.

People born with Down syndrome share some common features but they also inherit many of their own family's characteristics. This means they are as alike and as different from each other as the rest of the population. Every individual with Down syndrome has a different personality with different likes and dislikes.

Children born with Down syndrome have an increased risk of developing a wide range of ongoing medical and health problems including hearing and vision impairment, respiratory illness, thyroid malfunction, heart defects, gastrointestinal tract disorders, hypotonia (reduced muscle tone), musculoskeletal issues, skin conditions, leukaemia, epilepsy and Alzheimer's disease. These health issues often impair their physical and intellectual development.

Over the last 30 years, the average life expectancy of a person with Down syndrome has increased from less than thirty years of age to today when it is common to see people with Down syndrome living well into their sixties. It expected that this life span will continue to increase.

A positive supportive environment and help from family, friends and the community helps people with Down syndrome to develop to their full potential and lead fulfilling lives.