If you or someone you care about has a child with Down syndrome, or is pregnant with a Down syndrome baby, you may have many questions or feel overwhelmed by what this means. The most important thing that babies with Down syndrome need — just like any baby — is a loving, secure environment in which they feel nurtured and supported.

What is Down syndrome?

Down syndrome is the most common chromosomal condition that a baby can be born with. Around 1 in every 1,000 babies born in Australia has Down syndrome.

Down syndrome is also known as Trisomy 21. People with Down syndrome usually look different from other people and may have some difficulty learning new things.

What causes Down syndrome?

Normally, every cell in the human body — except egg and sperm cells — has 46 chromosomes. The egg and sperm cells normally have 23 chromosomes each.

The most common cause of Down syndrome is when an extra copy of chromosome 21 randomly appears in either the egg or sperm. At conception, when the egg and sperm meet, the extra copy of chromosome 21 grows throughout all of the embryo’s cells, giving them each 47 chromosomes instead of the usual 46.

Less commonly, the extra copy of the chromosome can appear in some of the embryo’s cells after conception. This is called mosaicism and results in some cells having 46 chromosomes and some having 47.

Another rare form of the syndrome is caused by ‘Robertsonian translocation’. This occurs when a piece of chromosome 21 breaks off and becomes joined to another chromosome before or after conception. In this case, the embryo’s cells will all have 46 chromosomes, but each cell still contains an extra copy of chromosome 21.

What are the most common features of Down syndrome?

Many babies with Down syndrome have one or more of the following features at birth:

• low muscle tone ('floppy' muscles)
• a flatter face with eyes slanting upward
• small ears and a wider neck than usual
• a single crease across the palm of the hand
• a gap between the first and second toes

Down syndrome is also associated with intellectual disability.

However, not everyone with Down syndrome will have all of these features.

What medical complications might come with Down syndrome?

About 1 in every 2 babies born with Down syndrome will have heart problems and approximately 1 in 10 will have gastrointestinal (gut) problems. Hearing and vision problems are also more common in people with Down syndrome.

How is Down syndrome diagnosed?

Pregnant women are offered routine antenatal tests at different times during pregnancy and for different reasons. These include screening tests, such as ultrasounds and blood tests, that can help estimate your baby’s risk of being born with a range of conditions, including Down syndrome.

Non-invasive prenatal testing (NIPT) is a new blood test that can be done as an alternative screening test.

Diagnostic tests (such as chorionic villus sampling or amniocentesis) will show whether a baby actually has Down syndrome.

After the baby is born, chromosome testing from a blood sample, may be done to confirm Down syndrome.

What is the treatment for Down syndrome?

There is currently no way to prevent or cure Down syndrome. Prenatal testing allows you and your family to make informed decisions, including ending the pregnancy. For this reason, before you have the test it’s a good idea to think about why you are choosing to do it, and how you will feel once you get the results.

Consider also who you want to discuss any important decisions with — your partner, a friend or family member, or a health professional such as your doctor or midwife are all good options.

Early diagnosis can also help you and your doctor continue to check your baby for complications and to act early if needed. Some people with Down syndrome may need surgery to repair heart defects or gut blockages. Medicines to treat thyroid disease may also be needed in some cases.

Children all learn and develop at their own pace. However, there are effective early intervention programs for children with Down syndrome that can help them reach their learning potential.

Resources and support

Down Syndrome Australia provides support, information and resources for people with Down syndrome and their families across Australia.

Support services include:

• information and advice about Down syndrome
• information about local support groups
• home visits
• new parent packs
• workshops and webinars
• online support groups for you and your family

A national phone number (1300 881 935) can connect you with your local state or territory Down syndrome organisation for further information.