NIPT (Non-Invasive Prenatal Testing)
NIPT is a new testing option available which is 99.5% accurate when screening for Down syndrome.
The non-invasive prenatal test (NIPT) has been available in Australia since 2013 and is a test by which fetal DNA can be assessed from a blood sample taken from the mother. It requires a simple maternal blood test taken from 10 weeks gestation, but can also be done at any time throughout the pregnancy.
The NIPT should always be preceded by an ultrasound to check fetal gestation and viability.
The testing is now done in Australia and results are available in about ten days. This test screens for:
Trisomy 21 (Down syndrome) - 99.5% accurate
Trisomy 18 (Edwards syndrome) - 97% accurate
Trisomy 13 (Patau syndrome) - 94% accurate
Sex chromosomes - 99% accurate
Triploidy - accuracy not documented
The accuracy of the test is reduced when the patients are:
- insulin dependent diabetics
- have high BMI
- are less than 10 weeks gestation
Failure of the NIPT increases the chance of aneuploidy by a factor of 9, so patients whose NIPT's have failed twice should be counselled and may consider invasive testing.
The failure rate of the NIPT is 8%.
The NIPT is a screening test to look at the chance of the fetus having Trisomy 13, 18, 21 and having problems with the sex chromosomes.
It should be noted that the NIPT does not replace the Nuchal Translucency screen at 12 to 13 weeks, but may be done in conjunction with it.
The importance of the 12 to 13 week Nuchal Translucency screen is that it also checks fetal structure (early morphology scan of fetus), assesses the chance of the patient developing early onset pre-eclampsia, low birth weight and premature delivery.