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Pregnant woman getting an ultrasound - Screening for Down syndrome

Pregnant woman getting an ultrasound - Screening for Down syndrome
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Screening for Down syndrome

Screening tests for Down syndrome are available during the first and second trimesters of pregnancy. These tests will only tell if your baby is at risk of Down syndrome. Further testing can then be done to provide a diagnosis.

Down syndrome is a genetic disorder that occurs very early in your pregnancy when your baby is first forming. While most people have 23 pairs of chromosomes, people with Down syndrome have an extra copy of chromosome 21.

There are 2 types of screening tests that are available that tell you if your baby might be at risk of having Down syndrome. Further diagnostic tests can then be done to confirm the results.

First trimester combined screening

This involves a blood test and an ultrasound scan

Women may be offered 2 ultrasounds at the beginning of their pregnancy:

  • dating scan between weeks 8 and 14 of pregnancy
  • nuchal translucency scan between 11 weeks and 13 weeks and 6 days of pregnancy (sometimes called the '12 week scan').

If you choose to be screened for Down syndrome, the dating scan and the nuchal translucency scan can be carried out at the same time, between 11 weeks and 13 weeks.

At the ultrasound scan appointment, the sonographer measures the thickness of the nuchal translucency (a pocket of fluid) at the back of your baby's neck.

You have the blood test between 9 and 12 weeks. The blood test measures the levels of two different hormones that occur naturally in your blood during pregnancy. When there’s a genetic condition the levels of these hormones are usually abnormal.

The information from the blood test is combined with your age and the nuchal translucency measurement and used to work out your individual chance of having a baby with Down syndrome.

Second trimester screening 

If it has not been possible for you to have the combined screening test in early pregnancy, you will be offered a different blood test between 14 and 20 weeks.

This test is sometimes called the 'triple test' or 'maternal serum screening' test (MSS) and measures proteins associated with pregnancy. This information is combined with your age and used to work out your individual chance of having a baby with Down syndrome.

Diagnostic tests

If the screening tests come back indicating that there is a risk that your baby may have Down syndrome, your midwife or doctor will explain the results to you and help you to decide whether you want to have further testing. One of your options will be to have a further diagnostic test which provides a definite answer.

The diagnostic test will either be by chorionic villus sampling (CVS) or amniocentesis. Your midwife or doctor will explain the result to you and help you to decide whether you want to have further testing.

Dealing with the results

It's always difficult when you're told that something is wrong with your baby, especially if you're faced with a painful decision about the future of your pregnancy.

Your midwife or doctor will make sure you see the appropriate health professionals to help you get all the information and support you need so you can make the right choices for you and your family.

Read more about caring for a child with Down syndrome.

Down Syndrome Association has information and services available to parents, including being able to speak to a parent of a child with Down syndrome.

You can also call Pregnancy, Birth and Baby on 1800 882 436 if you have any questions or would like to speak with a counsellor.

Last reviewed: February 2016

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Pregnancy - Pregnancy Topics - Screening tests for Down syndrome

Screening tests can be done to work out the chance that your baby has Down syndrome.They cannot tell for sure whether your baby has Down syndrome - they can tell if the risk of your baby having Down syndrome is higher than usual. If your baby has a higher risk than usual of having Down syndrome there are other tests that can then be done whichcan tell for sure.

Read more on Women's and Children's Health Network website

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Information on the down syndrome screening test including what down syndrome is, what the screening test will tell you, plus links to trusted resources.

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Maternal screening - Lab Tests Online AU

For a pregnant mother to assess the chance of her baby being born with an abnormality such as Down syndrome or spina bifida.

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Prenatal testing for Down syndrome

You may find this information helpful if you are considering having prenatal testing or if you’ve had a test that shows your baby may have or does have Down syndrome.

Read more on Down Syndrome Australia website

Diagnostic tests for your baby during pregnancy

A diagnostic test is used to confirm a chromosomal condition, such as Down syndrome, or a genetic condition in the baby.

Read more on WA Health website

Prenatal information | Down Syndrome Australia

Down Syndrome Australia provides prenatal support and information including a prenatal fact sheet that contains easy-to-understand, factual and balanced information for people considering prenatal testing or if a test shows that a baby may have or does have Down syndrome.

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Down syndrome - Lab Tests Online AU

Down syndrome (DS) is a congenital condition caused by an extra copy or piece of chromosome 21 in all or most of the affected persons cells. It is a group of signs, symptoms, birth defects, and complications that arise from an error in cell division that occurs before, or shortly after, conception. This error has a widespread effect on the physical and mental development of the affected person.

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What is Down syndrome?

Down syndrome is a genetic disorder characterised by mental and developmental impairments. The disorder is also known as 'trisomy 21' as it is caused by the presence of an extra copy of chromosome 21.

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12 Weeks Pregnant Appointment | Raising Children Network

Find out about the 12 week ultrasound to check baby's development, and risk for conditions like Down syndrome, sometimes called nuchal translucency test.

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What is Down syndrome? | Down Syndrome Australia

Our bodies are made up of millions of cells. In each cell there are 46 chromosomes. The DNA in our chromosomes determines how we develop. Down syndrome is caused when there is an extra chromosome. People with Down syndrome have 47 chromosomes in their cells instead of 46. They have an extra chromosome 21, which is why Down syndrome is also sometimes known as trisomy 21.

Read more on Down Syndrome Australia website

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