In the last three years, a test useful for prenatal diagnosis has become widespread in clinical practice: it is the fetal DNA test. "A new type of analysis that has aroused great interest, because it is not an invasive procedure", emphasizes the doctor Faustina Lalatta, head of the Medical Genetics Unit at the del Policlino Clinic in our city.
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What is the fetal DNA test and who can do it?
This test involves looking for DNA fragments that come from the placenta, and which is circulating in maternal blood from the XNUMXth week of pregnancy.
All future mothers can do it, but it must be remembered that today it is a test sold exclusively in the private sector. In fact, the Ministry of Health, despite having identified it as a test of great interest, has not yet accredited it.
Il cost of this examination is variable, there is a very wide offer: from a minimum of 600 euros to 1.100 €.
How does it work?
Currently, the exam identifies major chromosomal abnormalities: the trisomy of chromosome 21, which corresponds to Down syndrome; and then that of chromosome 13 or 18. In addition, it allows to identify the X and Y chromosome, which determine fetal sex.
How reliable is this test?
L'reliability is very high regarding trisomy 21, which corresponds to Down syndrome. Other positivity, such as trisomy 18 or 13 are less reliable: therefore, for a confirmation it will be necessary to do other in-depth examinations.
Since when can this be done?
The ideal, to perform fetal DNA, is to follow a path: it is not an exam to be done suddenly, at any gestational period. Technically, it can be done from the tenth week, but international and national guidelines say that it is imperative that the assessment of the translucenza nucale or, better yet, the Bi Test. So, the exam will be done around the twelfth week with this data already available.
Are there any risks?
There is no risk for the fetus. While, for the mother, the test could be a source of anxiety if there were any positives to be confirmed.
Another risk is that of give too large a value to this test: I have often heard women say that their gynecologist equated the fetal DNA test with villocentesis o amniocentesis. This is not true: it is about completely different procedures, with different diagnostic value, with different execution techniques.
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