NIPT – Non-invasive prenatal testing
What is NIPT?
The NIPT prenatal test is a non-invasive method for detecting possible fetal chromosomal trisomies after the 10th week of pregnancy. It is based on taking venous blood and further analysis of fetal DNA from the mother's blood. The test is completely harmless for both the pregnant woman and the fetus. The test cannot detect genetic mutations, chromosomal mosaicism and structural chromosomal abnormalities. With the non-invasive NIPT test, we determine the absence or possible presence of trisomies in the fetus without any risk and with a reliability exceeding 99%.
What do the test results show?
With the non-invasive NIPT test, we determine the presence or absence of the trisomy of chromosomes 21, 18, 13 and sex-linked chromosomal abnormalities. The reliability of the test exceeds 99%. A negative test result usually means that the pregnant woman is carrying a healthy fetus and that no other tests are required. If the result is positive, it is very likely that trisomy is present. In this case, the pregnant woman is advised to undergo additional testing that can confirm or deny the suspicion.
Why do a non-invasive NIPT test?
A combination of screening and diagnostic tests during pregnancy reveals chromosomal abnormalities. Currently, the most commonly used screening test method is the combined first-trimester screening test that measures hormones and nuchal fold thickness. If the test results show a high risk, the doctor will recommend a diagnostic test (amniocentesis) that reliably excludes or confirms the presence of a chromosomal trisomy. However, existing screening tests have a shortcoming: they lead to a large number of pregnant women being referred for invasive diagnostic tests, which generally determine that Down syndrome is not present in the fetus. In fact, the presence of a chromosomal trisomy is confirmed in only 3% of cases. Because of this, many pregnant women who carry a healthy fetus and are referred for additional invasive diagnostic tests needlessly expose themselves to the risk of miscarriage, which amounts to about 1%.
What is trisomy?
In a normal pregnancy and healthy fetal development, the fetus has 23 pairs of chromosomes or 46 chromosomes in each somatic cell. In the case of trisomy, an abnormality has occurred in the separation of chromosomes, which means that a certain chromosome is present in three instead of two copies. This means that there are 47 chromosomes in each somatic cell.
Risk for the presence of trisomy
LOW RISK for the presence of trisomy
If the result of the NIPT test is negative, chromosomal trisomy is almost excluded (the probability of absence of a trisomy exceeds 99%).
HIGH RISK for the presence of trisomy
If the results of the NIPT test indicate a high probability for the presence of one of the trisomies (T21, T18 and T13), this does not mean that the result is final. In high-risk cases, two methods are available to confirm or deny the presence of trisomy. Our doctors will advise you and suggest invasive prenatal diagnostics (amniocentesis). In the case of a high risk for the presence of trisomy, Podobnik SH bears the costs of the amniocentesis, and the final findings are completed quickly. Fortunately, such a procedure is required in an extremely small number of cases.
A non-invasive test does not detect all anomalies in fetal development, and is, therefore, not a substitute for detailed ultrasound examinations during the first and second trimester, which are crucial for the detection of fetal malformations.
Non-invasive prenatal diagnosis using maternal blood is performed in only a few genetic centers in the world. Podobnik Special Hospital was the first to make it available in Croatia as early as the beginning of 2013.
Depending on the laboratory where the test is performed, we distinguish several similar tests. We perform 4 tests at the Podobnik Special Hospital.
The prenatal NIFTY test was developed in the accredited medical laboratory of the company BGI (Hong Kong). The test has been validated; its reliability and specificity have been tested in several clinical studies, including the largest clinical study conducted on 146,000 pregnant women. The test can be done in a validated laboratory in Zagreb since 2019.
Qualified testing is performed on the Illumina platform and offers a number of packages with an overview of all chromosomes and the largest number of microdeletions. Testing is performed at the Veritas laboratory in Spain, while Qualified Focus is performed at a laboratory in Rome and includes the largest currently available array of chromosomal errors and monogenic hereditary diseases in the fetus, mother and father.
The Panorama test is patented in the Natera clinical laboratory in the USA. It also detects triploidies and a number of microdeletions.
The myPrenatal test is performed on the Illumina platform, and the Superior package includes the largest spectrum of chromosomal abnormalities – a review of all chromosomes and the largest number of chromosomal microdeletions that are the cause of numerous syndromes. Testing is carried out at the Veritas laboratory in Spain.
