At a glance
Also known as
Why get tested?
To evaluate the risk of your baby having Down syndrome
or a rarer chromosomal disorder
When to get tested?
NIPT can be done from about 10 weeks of pregnancy
A blood sample drawn from a vein in your arm
Confused about genetics?
See our Genetics Information page
What is being tested?
There are fragments circulating freely in our bloodstream (also known as cell-free DNA). During pregnancy, a small amount of this DNA comes from the baby in the womb (the fetus). NIPT measures the amount of DNA from the fetus circulating in the mother’s blood stream. More specifically, it measures the quantity of fetal DNA coming from chromosome 21,13,18, X and Y. If the baby has an extra one of these chromosomes, the test is able to measure this excess amount of DNA. This way, NIPT is able to detect chromosome conditions such as Down syndrome (due to an extra copy of Chromosome 21, or trisomy 21), Patau syndrome (trisomy 13), Edward syndrome (trisomy 18) and identify the sex of the baby.
How is the sample collected for testing?
A blood sample is obtained from the mother.
Is any test preparation needed to ensure the quality of the sample?
No test preparation is needed.
How is it used?
NIPT is used to assess the risk of a baby being affected by Down syndrome
or other less common chromosomal disorders
. It is ordered early in pregnancy in women who are concerned about having a child affected by trisomy 13, 18 or 21. This is a screening test. Any positive results need to be confirmed by a diagnostic test such as amniocentesis
or chorionic villus sampling
When is it requested?
NIPT is available to all women during pregnancy. NIPT has been assessed as a useful screening tool in pregnancies where the following risk factors are present:
- Maternal age >35 years of age at the time the baby is due.
- Abnormal first trimester maternal serum screen and nuchal translucency.
- A previous pregnancy affected by a chromosomal disorder.
- A fetal abnormality on ultrasound.
What does the test result mean?
NIPT is a more accurate test than other first or second trimester blood tests used for Down syndrome screening. When it is used in high-risk pregnancies in has sensitivity of around 99.5 per cent for detecting Down syndrome, i.e. less than one case in 100 will be missed by the test. It also has a very high specificity; it is very rare for the test to give a false-positive result. These figures may not be the same for women who are in the low risk group such as younger women and it is likely that false-positive and false-negative result rates will be higher. Also, the sensitivity and specificity of the test are not as good for rarer chromosomal disorders such as trisomy 13 and 18 and sex chromosome disorders. They are lower still for other microdeletion syndromes.
First trimester blood test and 12 week nuchal scan are still recommended to look for other structural or chomrosomal abnormalities.
Is there anything else I should know?
NIPT is only available through private laboratories. It is not covered by Medicare or private health insurance. The cost ranges from $489 - $1400 per test.
Very infrequently the test may not give a result as there may be insufficient DNA from the baby in the mother’s blood sample.
NIPT is not reliable in pregnancies with more than one fetus, or where a donor egg or embryo has been used.
Who performs NIPT testing?
Most pathology laboratories in Australia offer specimen collection for NIPT and may do the test themselves or send the sample to one of the specialist laboratories, in Victoria or overseas for testing. Depending on where the testing is done the results may take 5 -14 days.
Should I still have the first trimester ultrasound and blood test?
First trimester ultrasound remains an important screening tool for congenital abnormalities which may, or may not have a chromosomal cause.
NIPT can be used as a second-line screen following a combined first trimester ultrasound and blood testing, using the following principles:
- If the first trimester combined screen is low risk (risk less than 1 in 300) then recommend no further testing. The chance of having a baby with Down syndrome after a result in this range is very low. However, if you remain concerned, NIPT is a safe option.
- If the first trimester combined screen shows an increased risk, (risk greater than 1 in 300) then discussion with your GP or a genetic counsellor regarding the risks and benefits of chorionic villus sampling or amniocentesis compared to NIPT.
Last Review Date: March 15, 2016