what they are and when to do them
Fetal DNA testing and NIPT - non-invasive tests
THE prenatal genetic testing include a set of non-invasive screening tests that help to assess the risk of chromosomal abnormalities in the fetus starting in the first trimester of pregnancy. They are based on the analysis of ultrasound and biochemical parameters and, in the most modern tests, of cell-free fetal DNA circulating in the maternal blood. They do not replace invasive diagnostic tests, but They allow the identification of pregnancies at higher risk, reducing the unnecessary use of procedures such as chorionic villus sampling and amniocentesis. Their goal is to provide couples with more comprehensive information, along with a gynecologist-led process, to help them make informed decisions about further investigation.
THE prenatal genetic testing non-invasive, such as Combined Test (Bi-test) and Fetal DNA Test (NIPT – Non-Invasive Prenatal Testing), are designed to estimate the likelihood that the baby will have certain chromosomal abnormalities. Specifically, these tests focus on the most common and clinically relevant trisomies, such as Down syndrome (trisomy 21), Edwards syndrome (trisomy 18), and Patau syndrome (trisomy 13). Compared to invasive tests, screening tests do not carry a risk of miscarriage, as they are based on ultrasound scans and maternal blood samples. The information they provide is probabilistic: a low-risk result reduces the likelihood of chromosomal abnormalities, while an increased risk indicates the need to evaluate, together with the gynecologist, the possible use of chorionic villus sampling or amniocentesis. This balances safety, accuracy, and the need for confirmatory diagnoses only in selected cases.
how it works
nipt - test del dna fetale
Among the prenatal genetic testing, the Non-Intrauterine Fetal DNA Test (NIPT) represents the most recent and advanced method. It analyzes cell-free fetal DNA present in maternal blood, derived from microfragments of placental origin that circulate in the bloodstream starting in the first trimester.
With a simple venous blood sampling performed from the 10th week During pregnancy, it is possible to study the fetal chromosomal makeup for some chromosomal abnormalities and, depending on the test chosen, for some specific genetic conditions.
This noninvasive approach achieves very high levels of sensitivity, identifying the majority of cases of Down syndrome and a significant proportion of other trisomies, without exposing the pregnancy to procedural risks. Available NIPT tests may differ in the scope of the analysis (number of chromosomes assessed, additional panels) and the information provided. The result, expressed in terms of increased or reduced risk, must always be interpreted by the gynecologist, who may recommend confirmation through invasive diagnosis if the result is positive.
Times, types of tests and interpretation of the results
who are they aimed at?
Generally speaking, the prenatal genetic testing They can be offered to all pregnant women, regardless of age. They are particularly useful when:
- there are no risk factors that would directly indicate an invasive diagnosis
- first trimester screening showed intermediate or increased risk
- maternal age is more advanced
- there is a family history of chromosomal abnormalities
- there are precedents of repeated miscarriages
- the pregnancy is single or bichorionic bigeminal, even if obtained with assisted fertilization techniques, including heterologous ones
Conversely, fetal DNA tests are not indicated in certain specific situations, such as complex monochorionic pregnancies or gestations with three or more fetuses, where the interpretation of the results is less reliable. In any case, the choice of screening program is personalized based on the couple's medical history and the characteristics of the pregnancy.
THE prenatal genetic testing Non-invasive tests require relatively short processing and reporting times. Fetal DNA sampling is generally performed starting from the 10th week, and results are available, on average, within a few working days. The various options available (such as the PrenatalSAFE, Neobona, Aurora panels, and other equivalent tests) differ mainly in:
- the extent of the chromosomal panel analyzed
- the possibility of including or not including microdeletions or specific genetic conditions
- the amount of additional information provided to the couple
The report indicates an increased or reduced risk for the abnormalities considered. It is essential to remember that NIPT is not a diagnostic test: a high-risk result requires confirmation with chorionic villus sampling or amniocentesis, while a reassuring result reduces the likelihood of pathology but does not eliminate it completely. Therefore, the results should always be communicated in a structured consultation with the gynecologist.
The role of the gynecologist in the prenatal screening process
The integration of the prenatal genetic testing In the obstetric process, a thorough initial assessment of the couple's medical history, risk factors, and expectations is required. The gynecologist explains the characteristics, limitations, and potential of the various screening tests available, helping parents choose the most appropriate option based on the gestational age and clinical picture.
Whether the result is positive or uncertain, the doctor guides the couple in understanding the meaning of the result and in choosing confirmatory tests, such as chorionic villus sampling or amniocentesis, which allow for a definitive diagnosis. In this way, non-invasive tests become a support tool for the entire prenatal process, rather than an isolated test, integrating into a broader framework of ultrasound checks, obstetric visits, and laboratory tests.
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