Cell-free fetal DNA testing for fetal chromosomal abnormalities
cffDNA, NIPS (non-invasive prenatal screening)
NIPT is a screening test which has better performance than other first or second trimester blood tests used for Down syndrome screening which are based on measuring the concentration of a number of biochemical markers in the mother's blood. It has a 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. When NIPT is used in pregnancies which have a very high pre-test risk of Down syndrome (trisomy 21), false-positive results are not common (althought still possible). However, for women who are in a lower risk group such as younger women, it is known 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 ultrasound scan are still recommended to look for other structural or chromosomal abnormalities.
NIPT is currently available primarily through private laboratories. It is not covered by Medicare or private health insurance. The cost is approximately $400-500 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. This is more likely if the test is conducted in very early pregnancy.
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 (cFTS), using the following principles (as a guide only- the optimal screening pathway for each patient likely varies depending on individual clinical circumstances and should be adapted for each patient in consultation with your medical practitioner):
Down Syndrome Screening, Maternal Screening, Amniotic Fluid Analysis, Chromosome studies
Last Review Date: October 14, 2022