What is non-invasive prenatal testing (NIPT)?
Non-invasive prenatal test (NIPT) assesses the risk of a fetus being affected by Down’s syndrome, various trisomies and other serious genetic conditions (e.g. microdeletions) by analysing cell-free fetal DNA from a sample of maternal blood. Current modern genomic technologies, like next generation sequencing (NGS) and microarrays, allows to count the number of fragments of the specific chromosomes. Using sophisticated bioinformatic algorithms the fetal/maternal cfDNA ratio is then calculated, hence providing a risk of an affected pregnancy.
The non-invasive prenatal screen is significantly safer and easier, and therefore becoming one of the most rapidly adopted tests in prenatal care.
Since NIPT is non-invasive, therefore it poses no risk to the mother or baby.
The main advantages of NIPT are that it can be carried out much earlier in pregnancy compared to other tests and that the procedure does not carry any risk of miscarriage. The test only requires a blood test from mum, rather than having to take a sample directly from the womb as in other types of invasive prenatal diagnosis, such as chorionic villus sampling (CVS) or amniocentesis.
Two main types of NIPT methods are commercially available:
- NGS counting methods (whole or targeted approach) and
- NGS single-nucleotide polymorphism (SNP) based methods.
In terms of test administration two types of NIPT categories are available – centralized (performed in a single location; a test is sold as a sample collection package kit which is shipped overseas) or decentralized (performed in smaller laboratories; tests are sold as reagents kits to laboratories). Test administration in a local laboratory generally means shorter turnaround time (TAT).
Cell-free DNA NIPT should not be regarded as “just a simple blood test” - it is a genetic test with tremendous implications and consequences if misunderstood, therefore our website will serve you as a source of comprehensive and credible information enabling you to make best informed choices regarding NIPT.
Although NIPT's are generally TEN times (10x) more accurate than standard screening tests, in some situations samples can not be validly assessed:
- earlier pregnancy, than recommended by manufacturer (typically before 8-10 week)
- twins or multiple pregnancies, including unrecognized or vanishing twin
- placental or maternal mosaicism
- women who have undergone one of the following treatments during 12 month: blood transfusion, immune therapy, stem cell therapy, transplantation, radiation therapy.
- failure to extract adequate material for analysis (low cfDNA level).
Additional things to keep in mind regarding NIPT results:
- The NIPT tests mostly screen for only the common trisomies and, if optionally requested, sex chromosome comopsition (gender determination) as well as microdeletions.
- The accuracy of test to assess possibility of Down syndrome, Trisomy 18, Trisomy 13, and other chromosome conditions varies widely. Please use our MyAdvisor Tool to get better insight of the best options available to you.
- Not all NIPT labs screen for the same conditions - in our website you can compare various NIPT's and find which one is the most suitable and reliable for you.
- NIPT can often tell you if the baby is a boy or a girl, however, there is also a small possibility that this testing will predict gender incorrectly, which can result in false positive results.
- NIPT does not look for all chromosomal disorders or birth defects. Therefore a negative cfDNA NIPT test result does not ensure an unaffected pregnancy.
- NIPT does not assess a risk of neural tube defects or ventral wall defects, for which maternal serum alpha-fetoprotein (AFP) screening or ultrasound evaluation maybe necessary.
- Women who test positive with NIPT still need to confirm the result through invasive diagnostic testing such as amniocentesis, especially if they would consider terminating pregnancy.
- Women whose results are not reported, indeterminate, or uninterpretable (a “no call” test result) from cfDNA NIPT screening should receive further genetic counseling and be offered comprehensive ultrasound evaluation and diagnostic testing because of an increased risk of aneuploidy.
- Sometimes NIPT can find evidence of other health conditions in mom or baby that we are not expecting (for instance, the testing may reveal evidence of potential cancer in mother or another genetic condition in baby that isn’t on the list of typically screened for conditions).
- Usually NIPT screening is not recommended for women with multiple (more than two) gestations.
Analysis of fetal cfDNA is regarded as the next frontier of the genomic revolution and prenatal DNA sequencing (i.e. screening) was selected by MIT Technology Review as one of the breakthrough technologies of the 2013 year which are believed to expand human possibilities.