Amniocentesis and CVS are, by definition, the two invasive prenatal diagnostic procedures. Those that scare all women a little, both for the execution of the exam itself, and for what it could reveal, namely important chromosomal anomalies. Let's try to understand how these two methods work with the help of Patrizia Curcio, specialist in maternal-fetal medicine, with a specific training at King's College in London.
Dr. Patrizia Curcio
Curcio, what are amniocentesis and CVS?
“They are the invasive methods that allow to know the fetal chromosomal map (the number of chromosomes of each human being is 46). They are invasive as they involve a risk of miscarriage related to the procedure itself. The expected miscarriage risk is 1% for both techniques. Today there are highly reliable non-invasive tests (research of fetal DNA in maternal blood, cell free DNA) for Down Syndrome, but the high cost limits their use in particular situations and above all they should always be recommended in association with the screening of the first. quarter".
Many women are still very afraid of having these tests for the risk of abortion. Are these fears justified?
“The fear of 'loss' is above all linked to the imagery of the invasive word that evokes a kind of damage caused. In fact, the international scientific communities agree that the risk should be reviewed as a recent study by a Danish group concluded that the risk of invasive diagnosis can be allocated between 0,1-0,2% with experienced operators. This means that the risk is lower than previously considered and that every woman should receive adequate information on the risks and benefits that derive from a procedure correctly performed by an expert operator ".
What are the two techniques able to diagnose and what are the differences?
“Both methods give overlapping information (there are possible, albeit rare, technical problems related to the results of the laboratory as regards the chorionic villi). In reality, what substantially changes is the material taken and the gestational period in which it is possible to carry them out. They detect anomalies in the number and shape of chromosomes. Each of these variants can be associated with a specific disease. Villocentesis is performed at 11-13 weeks and fragments of the placenta are collected. The amniocentesis is carried out at 16 weeks and amniotic fluid is collected ".
How are the exams performed? How long does it take to get the result?
“The techniques of the procedures are linked to the operator and, especially for CVS, there are small differences between one operator and another. They consist in the introduction of a needle, through the maternal abdomen, reaching the placenta or a pocket of amniotic fluid, far from fetal parts. I use a local anesthetic in the case of CVS. Both last a few minutes. They don't cause pain, but fear often makes the procedure a time of profound emotional tension. The result of a chromosomal map is obtained on average 15 days after sampling, but there is the possibility of an extremely reliable laboratory technique (QF-PCR) for the most frequent chromosome anomalies, such as trisomy 21 (Down's Syndrome), which provides a result 24-48 hours after the procedure ".
When are they especially recommended?
"The indications for invasive diagnosis are many and depend on the gestational age in which they are performed. Maternal age is no longer considered a risk factor for accessing an invasive test, but the risk is recalculated after the first trimester screening. Therefore, regardless of age, a group of patients at risk at first trimester screening is selected, usually for increased nuchal translucency or even for the presence of structural defects already visible at this early stage. an invasive procedure is proposed is one in which we find defects visible only at the time of the morphological examination Finally, there remains the group of patients with genetically transmissible diseases who usually resort to CVS to have an early response on the health of their future child. The material coming from CVS or amniocentesis can be stored and reused in the case of laboratory investigations more sophisticated atoriums that may need to be carried out during pregnancy. The definitive diagnosis is not always direct and it often takes time to identify some pathologies ".
What should a woman do after performing them?
“After the procedure, absolute rest with bed rest is not required and the possible, albeit rare, appearance of high fever, sentinel of the development of chorionamnionitis, intrauterine infection induced by the procedure, must be monitored. In this case and in the case of severe pain, blood loss or fluid, it is absolutely necessary to contact the reference gynecologist or go to the hospital. Small losses and mild contractions can be normal and without any consequences. Antibiotic therapy before invasive diagnosis is not part of the protocol recommended by international guidelines ".
What is your approach to the couple in communicating a negative diagnosis?
“'Communicating' to a future mother that something is wrong I think is one of the most painful things to face because in everyone's imagination, pregnancy is, by definition, a happy event. There are pathologies that can be treated surgically, others clinically, still others involve sequelae of a neurological, motor, psychic, aesthetic ..., others fatal. Most of the time a woman has a pathological result she is already informed of the presence of some sign that motivated the procedure. The situations to be faced are the most diverse since the variety of clinical pictures has a broad spectrum and because the emotional level is profoundly different in every woman. Teamwork is often the only one that allows us to give a couple all the information they need to be able to choose and that somehow alleviates the despair at what has touched them. I am not a conscientious objector and I find it difficult to imagine that a woman can be impartially accompanied through the painful process of voluntary interruption. In fact, the Del Paesena law provides that, in serious cases, it is possible to resort to abortion up to about 22 weeks and three days. This, I will tell you, is the most difficult question because it touches intimate notes, because it involves empathy, esteem, professionalism, rigor… an explosive mix that makes the other feel they can 'trust and trust' ".