Novel Prenatal Testing (NIPT)
What is NIPT? We now know that some of the baby's DNA circulates in the mother's blood during pregnancy. DNA is the substance that makes up our chromosomes and contains our genetic information. By looking at the baby's DNA found in the mother's blood, we are able to identify if the baby is affected by chromosomal conditions such as Down syndrome. The baby's DNA is lost from the mother's bloodstream within hours of the baby's birth, so testing is specific to the baby in that pregnancy. When is NIPT offered? NIPT is offered based on a positive screening test for Down syndrome (FTS or Quadruple Test). As an alternative to invasive tests such as Amniocentesis or CVS. How is NIPT performed? The test is performed from a sample of the mother's blood. About 10 ml (roughly one tablespoon) is taken from the arm as a normal blood test. The blood is then sent to a laboratory for testing in a special package. When is it time to do NIPT? There is only enough DNA in the mother's blood to perform the test from 10 weeks of pregnancy, so the test cannot be performed earlier. First, you will need to undergo an ultrasound scan to determine exactly how many weeks you are pregnant and whether there is more than one baby in the womb (for example, twins) and to rule out fetal abnormalities. How accurate is NIPT for Down syndrome? NIPT for Down syndrome is more than 99% accurate. This means that the test will detect more than 99 out of 100 cases of Down syndrome, so there is a very small chance that the test will miss an affected pregnancy. Although the test is highly accurate, there is still a very small chance (around 1 in 300) of an incorrect result. So if the result of your NIPT predicts that the baby has Down syndrome, you will be offered an invasive test such as Amniocentesis or CVS to confirm the result. How long does it take to get NIPT results? This is usually within 2 weeks after the lab receives your sample. In a very small number of cases, the laboratory may not be able to obtain your results. This may be because there was not enough of the baby's DNA in the blood sample to perform the test. If this happens, you will be asked for a second blood sample so that the test can be repeated; no additional costs will be charged for this retesting. What are the possible outcomes? Very unlikely to be affected - negative screening Your child is very unlikely to have Down syndrome, Edwards syndrome or Patau syndrome. You will then continue with your normal care during pregnancy. Presumed disability - positive screening It is very likely that the child suffers from Down syndrome, Edwards syndrome or Patau syndrome. You will be offered an invasive test to confirm this result. Inconclusive / Failed Result Because this is a new test, we occasionally get an inconclusive or "unclear" result. If we do not get a clear result, we will inform you and offer you another NIPT test. How safe is NIPT? The test is a blood test taken from the arm like a normal blood test. The test therefore poses no significant risk to you or your baby. As with all blood tests, there may be some bruising in the area where the blood sample was taken. What is the disadvantage of NIPT? It is still a very expensive test worldwide. Costs are expected to gradually decrease as technology becomes more widely used and advances.Non Invasive (NIPT) Prenatal Testing