What is NIPT?
NIPT is a maternal blood test detecting foetal DNA fragments in maternal blood to screen for some of the chromosomal abnormalities. It is available from 10 weeks.
What does the test screen for?
• Trisomy 21 (Down Syndrome) with 99% accuracy.
• Trisomy 18 (Edward’s Syndrome) with 98% accuracy.
• Trisomy 13 (Patau’s Syndrome).
• Sex chromosome abnormalities (you may know the gender of the baby if you wish).
However NIPT is not intended to replace other prenatal screening, which is also able to offer accurate dating, recognition of structural anomalies and identification of multiple pregnancies. Part of the first trimester screening (FTS) is the PAPP – A test, a low reading is able to recognise pregnancies at risk of pre-eclampsia and foetal growth restriction. It is not able to detect all the chromosomal abnormalities found by amniocentesis.
Who is the test for?
NIPT is most useful when used for patients at intermediate to high risk (1/50-1/1000). The current recommendations are that NIPT is offered to women with a high risk of an affected pregnancy.
If the NIPT returns a negative result, it should be interpreted as meaning that it is very unlikely that the foetus is affected and no amniocentesis is required. If a positive test is returned, it is still recommended that amniocentesis is performed since false positives have been reported.
How much does the test cost?
This testing is not currently funded by Medicare. All major pathology laboratories offer this testing privately and a cost of this test range between $ 500-850.
Limitations of the test
If there is a low amount of foetal DNA in the maternal blood sample (2-5 % cases), the NIPT cannot be reported. The Sample may need to be repeated.
Some of chromosomal abnormalities that would have been an incidental finding of a cytogenetic test will not be detected.
If a positive test is returned, it is still recommended that amniocentesis is performed since false positives have been reported.