What is Down syndrome?

Two women chatting outdoors together.

Down syndrome is a genetic disorder that occurs when a baby is born with an extra copy of chromosome 21.

The human body has trillions of cells, and within each cell is a thread-like structure made up of DNA, called a chromosome. Chromosomes are what determine how a baby’s body develops and functions during pregnancy and after birth.

Most people have 23 pairs of chromosomes in each of their cells (46 in total), but people with Down syndrome have 47 chromosomes in their cells, i.e. they have an extra chromosome 21. This extra copy changes how the baby’s body and brain develop, which may cause intellectual and learning disabilities as well as physical challenges for the person as they grow.

However, it’s important to remember that:

  • Down syndrome is a genetic condition
  • Down syndrome is not an illness or a disease
  • It is a lifelong condition and there’s no cure for it
  • As a genetic disorder, it cannot be prevented and no one is to blame
  • Each person with Down syndrome is a unique individual with their own personality, passions, strengths and weaknesses, just like anyone else
  • They also have their individual needs for support as they go through life.

People with Down syndrome may have physical features such as upward slanting eyes, a slightly flattened face, smaller hands, feet and ears, and a degree of intellectual disability. However, not everyone with Down syndrome looks ‘the same’, as a matter of fact, those with Down syndrome have more features in common with members of their family, just like anyone else.

Forms of Down syndrome

The three forms of Down syndrome are:

  • Trisomy 21: Found in 95 percent of people with Down syndrome. In Trisomy 21, every cell in the body has an extra chromosome 21.
  • Mosaic Down syndrome: Found in around two percent of people with Down syndrome. An extra chromosome is found in only some of the cells, whilst the other cells have the standard genetic makeup.
  • Translocation Down syndrome: Found in about three to four percent of people with Down syndrome. Part of chromosome 21 has detached and then translocated (attached) to another chromosome.

What causes Down syndrome?

Although, as explained above, how Down syndrome occurs is known. However, it’s not known as to why it occurs. It’s caused by a random biological error at the time of conception. Usually, a person has two copies of chromosome 21, but in a baby with Down syndrome, there are three copies, as mentioned earlier.

One of the factors that indicates an increase in risk for Down syndrome is women giving birth after the age of 35. However, approximately 70 percent of babies with Down syndrome are born to mothers aged 35 or younger, as it’s believed that there are many more births among younger women.

Down syndrome newborn diagnosis and screening

At or after birth, parents can opt for chromosome testing, done from a blood sample to confirm or rule out Down syndrome. Non-invasive prenatal testing (NIPT) is used to determine the possibility of Down syndrome in the first trimester of pregnancy.

NIPT is performed by a maternal blood test from the 10th week and does not pose any risk to the foetus. It’s important to note, however, that NIPT can only indicate an increased risk of the baby being born with an abnormality. It can’t provide a conclusive result.

The other two tests — Chorionic villus sampling and amniocentesis — are not screening, but diagnostic tests. Learn more about how a test is done for Down syndrome.

Down syndrome life expectancy

In Australia, the average life expectancy for a person with Down syndrome is 60 years. The syndrome may come with medical challenges involving the heart and lungs, gastrointestinal tract, sensory impairment, immunity, mental health, dental issues and hormonal problems, among others. Previously, life expectancy was much shorter but thanks to incredible medical advances, more people with the disorder are living a lot longer.

Support for people with Down syndrome

Most people with Down syndrome are able to lead normal lives, just like anyone else. Some might need additional support, owing to the physical and mental challenges that may accompany the condition.

Through Mable, children and adults with Down syndrome can access a variety of support options to achieve their goals and lead fulfilling and enjoyable lives. Independent support workers on Mable can offer support with social engagement, learning a new skill, capacity building to become more independent, supporting a person in their place of employment, and much more.

Natalie says the support her son Max receives via Mable has made her feel “like I’m in control again”. And Mable client Paige who lives with Down syndrome teaches dance classes to people with disabilities.

Children under the age of seven can receive NDIS funding through Early Childhood Early Intervention. Those with Down syndrome who are above seven years of age have to meet eligibility requirements for NDIS funding. If you’re approved for NDIS funding, you can use it to find support workers through Mable. Even if you’re not eligible for NDIS funding, you can connect with support workers via Mable and choose to pay privately.

World Down Syndrome Day

World Down Syndrome Day is celebrated every 21st March. The date was chosen because the number 21 is significant.

To celebrate World Down Syndrome Day, people around the world host morning teas or hold Lots of Socks events. They encourage others to wear bright, colourful socks and make as much of a visual impact as possible with their socks. It’s a fun and cheerful conversation starter, to get people talking about Down syndrome.

October is celebrated as Down Syndrome Awareness Month in Australia, through Step Up events.


Approximately one in every 1,100 babies born in Australia will be born with Down Syndrome. Annually, that’s around 290 new babies. No data is collected nationally about the number of people with Down syndrome in Australia. However, an estimate based on Western Australian data puts the figure at approximately 5.14 people for every 10,000 people, nationally.

For a person with Down syndrome in Australia, average life expectancy is 60 years of age.

Yes, pre-screening during IVF can test the embryo for Down syndrome.

Down syndrome is not a disease or an illness. It’s a genetic condition involving chromosomes (bundles of genes), and as such, it cannot be cured.

Adults with Down syndrome may need support to be able to live independent lives. While they are at greater risk of a number of health and medical conditions, they can work and earn an income, enjoy positive relationships, and may have children of their own.

No, Down syndrome is a lifelong genetic disorder that occurs at conception.