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N.I.P.T for Healthcare Professionals

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What is a NIPT?

A non-invasive prenatal test (NIPT) is an advanced screening test using DNA in the mother's blood to estimate the risk of a fetus having Down’s syndrome, Edwards' syndrome and Patau’s syndrome. There are many different NIPTs on the market, but the majority will screen for these three syndromes. Edwards’ and Patau’s syndrome are much rarer than Down’s syndrome but are very serious and many affected babies die before or soon after birth. Trisomies occur when three, instead of the usual two, copies of a chromosome are present.

Traditional screening offered during the first trimester of pregnancy is currently called the combined test. This is an ultrasound scan to measure the nuchal translucency (NT), combined with a blood test. This is less accurate than NIPT, detecting about 85% of babies with Down’s syndrome. Our test has a higher detection rate than the combined test. It is also better able to exclude false positives. This is when the test reports the baby is at a high risk of having Down’s syndrome but is actually unaffected. The test is much better at ensuring the babies are truly high risk. This allows the doctor to only refer the mother for an invasive test when it is likely the baby is affected. This means fewer healthcare professionals will undergo unnecessary invasive follow-up procedure such as amniocentesis or CVS which can be stressful, painful and may carry a small risk of miscarriage.

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How Does It Work?

From 10 weeks gestation a small blood sample is taken from the mother’s arm and sent to a local laboratory for analysis with NIPT. During pregnancy, the placenta leaks cell-free DNA which circulates in the maternal bloodstream. As a result, a maternal plasma sample contains a mixture of placental and maternal circulating DNA. The DNA from the mother’s blood is extracted and the test is performed on this small amount of DNA.The NIPT directly measures the amount of cell-free DNA and can detect small changes in the DNA ratio between the maternal and placental-fetal cell-free DNA when a fetal trisomy 21, 18 or 13 is present.

This trisomy figure is then combined with the prior risk (by default this is the mother’s age but the result of the First Trimester Combined Test (FTCT) can be used instead) to calculate the probability of the fetus being affected.

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Interpreting Results

  • 1. Low Risk: it is very unlikely the pregnancy is affected by trisomy 21, 18 or 13
  • 2. High Risk: the pregnancy is at increased risk for trisomy 21, 18 or 13 and the result should be confirmed by a follow-up invasive procedure, such as an amniocentesis or CVS.
  • 3. No Result: very occasionally there is insufficient placental DNA in the sample to obtain a result. Women may be asked back by the healthcare provider for a further blood sample.
Fetal sex determination

Our tests offers optional testing to determine the baby’s sex. A “sex determination failure” result may be reported if there is insufficient data to support the sex determination analysis. A failed result does not reflect on the quality of any other result generated by the IONA® test. Please note that the sex determining technique is not a screening test for rare sex chromosome conditions and is not currently available for multiple births except for identical (monochorionic) twin pregnancies. We therefore recommend that fetal sex determination is confirmed by ultrasound.

Fetal sex determination is only available for singleton and monochorionic twin pregnancies. It is only offered in regions where fetal sex determination is permitted.