You will be offered the NIPT screening test if you have a higher chance result from combined or quadruple screening and you are having only one baby or twins.
NIPT is a further screening test that is more accurate than the combined or quadruple test. It will not give a definite result. It is a blood test taken from you in the usual way – your blood will have your DNA (genetic material) in it and some of your baby’s DNA in it which is released from the placenta (afterbirth). The blood is sent to the laboratory and screened for Down’s syndrome (T21), Edwards’ syndrome (T18) and Patau’s syndrome (T13). If there is more DNA than expected for chromosomes 21,18 or 13 in your blood, it could mean that your baby has Down’s syndrome, Edwards’ syndrome or Patau’s syndrome. The result will tell you whether there is a low or high chance that your baby has one of the conditions. This test will not give a result for any other conditions, or the sex of your baby. If you choose this test it takes about two weeks to get the result.
The reason why this test is not 100% accurate is because it tests the DNA from the placenta and, in rare cases, this is not identical to the baby’s DNA. This is called confined placental mosaicism.
This test can be performed up to 20 weeks of pregnancy.
You will be unable to have the NIPT if:
Your midwife will be able to talk to you about this.
As NIPT is a screening test, it will not give you a definite result. Instead, it will give you a:
NIPT will give an accurate result for most women who choose to have the test, but there can be false positive and false negative results.
NIPT may also be less accurate in a twin pregnancy.
A false positive result means getting a high chance result when the baby does not have the condition.
A false negative result means getting a low chance result when the baby does have the condition.
Most women who have a NIPT will receive a low chance result for Down’s syndrome, Edwards’ syndrome or Patau’s syndrome. If you receive a low chance result, you will not be offered an invasive test (chorionic villus sampling (CVS) or amniocentesis). For most women the result is accurate.
If you have a high chance NIPT result for Down’s syndrome, Edwards’ syndrome or Patau’s syndrome, you will be offered an invasive test (chorionic villus sampling (CVS) or amniocentesis) or you may choose to have no further testing.
NIPT is less accurate in finding babies with Edwards’ syndrome or Patau’s syndrome than it is for Down’s syndrome.
Around 0.3% (1 in 300) of tests will not give a result, often because there are not enough of the baby’s cells in your blood. In this case you will be offered an invasive test to give you a result. Your midwife will be able to talk to you about this
You should discuss your individual result of your combined or quad test with your health professional before deciding on further testing.