What is the NIPT test?
The NIPT (or Non-Invasive Prenatal Diagnosis Testing) analyses cell free DNA in maternal blood and gives a strong indication of whether the fetus is at high or low risk of having Trisomy 21 (Down’s Syndrome), Trisomy 18 (Edwards Syndrome) or Trisomy 13 (Patau Syndrome).
The test identifies 99%, but not all, of the fetuses with Trisomy 21, 97% of fetuses with Trisomy 18 and 92% of fetuses with Trisomy 13.
If you decide to have the test you will be asked to sign a consent form by one of our doctors or an appropriately trained member of our staff. We will then draw a small amount of blood from a vein in your arm. This may cause some discomfort but the sample is usually taken very quickly. Sometimes there can be some bruising after a blood sample is taken.
How is NIPT different from the combined/quadruple test?
Although both tests involve a sample of maternal blood, NIPD analyses the cell-free DNA in the mother’s blood, whereas the combined and quadruple test analyses the mother’s hormone levels. With more than 98% accuracy, NIPT is more accurate than the first trimester combined test or second trimester quadruple test for estimating the chance of the risk that the baby has Down’s Syndrome.
What is Trisomy 21, 18 or 13?
In humans, there are 23 types of chromosomes and most people have a pair of each one of these chromosomes (therefore a total of 46 chromosomes). In Trisomy, there are three rather than two of a particular chromosome (total of 47 chromosomes). The most common trisomies are those of chromosomes 21, 18 and 13.
Trisomy 21 is found in about 1 in 700 births and the risk increases with maternal age. The condition is associated with intellectual disabilities and some physical defects, most commonly heart abnormalities. The life expectancy is about 60 years.
Trisomies 18 and 13 are found in about 1 in 7,000 births and the risk increases with maternal age. The conditions are associated with severe mental handicap and several physical defects. Most affected individuals die before or soon after birth and they rarely survive beyond the first year of life.
Who can have the NIPT test?
The NIPT test can be performed in women carrying one or two alive fetuses at any stage in their pregnancy from 10 to 32 weeks.
When do I expect to get the results?
The results from the test will generally be available within two weeks and we will notify you as soon as we receive them by phone and email/letter.
In about 5% of cases the test does not give a result. This is due to technical problems with the analysis of the sample and does not suggest that there is a problem with the baby. If you want you can have the test repeated (at no cost) and there is a 50% chance that the test will give a result.
What would the results show?
If the NIPT test shows that there is a high risk that the fetus has Trisomy 21 or 18 or 13 it does not mean that the fetus definitely has one of these defects. If you want to be certain if the fetus has one of these defects you should have CVS or amniocentesis.
If the NIPT test shows that there is a low risk (less than 1 in 10,000) that the fetus has Trisomy 21 or 18 or 13 it is unlikely that the fetus has one of these defects.
Do I need to have any other tests?
The NIPT test does not provide information on other rare chromosomal abnormalities. If the scan at 11-13 weeks shows a high nuchal translucency (more than 3.5 mm) or major defects, such as exomphalos, holoprosencephaly, heart abnormalities or megacysis, the risk for somerare chromosomal defects may be high. In such cases you may choose to have CVS or amniocentesis.
The NIPT test does not provide information on physical defects, such as heart or brain abnormalities and spina bifida, or fetal growth. It is therefore advisable that you still have nuchal ultrasound scans at 11-13 weeks and at 20-22 weeks to examine the fetal anatomy and at 32-36 weeks to examine the fetal growth.