What is the Non-Invasive Prenatal Test (NIPT)? During pregnancy, some of the baby’s DNA passes into the mother’s bloodstream. The non-invasive prenatal test (NIPT) analyses the genetic information contained in this fetal DNA to screen for a number of chromosomal abnormalities. The NIPT involves a simple blood sampling from mother and can be done from 10 weeks into the pregnancy and there has no risk to the mother and fetus.
What does it test for? The NIPT, a safe and highly effective way of screening for chromosomal abnormalities in fetus that include: • Down syndrome (trisomy 21) • Edwards syndrome (trisomy 18) • Patau syndrome (trisomy 13) • Turner syndrome (monosomy of X) and other sex chromosomal aneuploidies
Some laboratories also report the gender of the baby and look for problems with the sex chromosomes. The test detects many chromosomal abnormalities, but not as many as a diagnostic test such as amniocentesis. It cannot screen for single gene disorders such as cystic fibrosis, thalassaemia or sickle cell anaemia.
Why have an NIPT? •The NIPT is highly sensitive and detects more than 99% of cases of Down syndrome. But it is still a screening test rather than a diagnostic test. This means it can only tell you whether there is an increased risk of having a baby with an abnormality, rather than give you a definitive answer.
The only way of knowing for sure whether your baby has Down syndrome is to have a diagnostic test such as chorionic villus sampling (CVS) or amniocentesis.
You might choose to have an NIPT test if: • Your combined first trimester screening test shows that you are at increased risk of having a baby with Down syndrome, • The age of the mother (or egg donor) at the time of pregnancy is over 40 years, • Nuchal Translucency Measurement is equal or greater than 3.5 mm, • You did not have the combined first trimester screening test because it was too late or the test wasn't available in your area • You want to be sure you are at increased risk before you opt for diagnostic tests such as amniocentesis or CVS, which carry a small risk of miscarriage • You are at increased risk (for example, if you are older or you have previously had a baby with Down syndrome or another chromosomal condition), • In high-risk twin pregnancy during COVID-19 pandemic when:
What to expect from your NIPT results: It can take up to 2 weeks to get the result of your NIPT. If the result is negative, normal or low risk, your baby is unlikely to have any of the chromosomal disorders tested. If the result is positive, abnormal or high risk, this means your baby is likely to be affected. If you have an abnormal NIPT result, a diagnostic test such as CVS or amniocentesis can confirm the result. You should discuss your options with your doctor, midwife or genetic counsellor.
Who cannot have the NIPT test? • The NIPT test is not suitable if you have cancer or chromosomal abnormalities including Trisomy 13, 18 and 21. • NIPT cannot be performed in multiple pregnancies other than twins. • NIPT cannot be performed if you have had an organ transplant or received stem cell therapy or immunotherapy within the last 12 months. • NIPT cannot be performed if you have had a blood transfusion within the last 3 months. • This article has been approved by Dr. Mohammadreza Zamaniyan.