La villocentesis (chorionic villus sampling) is an invasive examination similar to amniocentesis which serves to highlight any chromosomal abnormalities of the fetus. Let's find out what this test is, how risky or accurate it can be and when it should be done.
What is Villocentesi
As explained by the Ministry of Health, this is a prenatal diagnostic examination which consists in the removal of a very small part of wild corial, which are nothing more than fragments of the tissues of the placenta containing pluripotent fetal stem cells, through the use of a very thin needle that is inserted under the navel.
The exam does not require local anesthesia, is performed under ultrasound monitoring and in aseptic conditions, to limit any risk of infection.19 PHOTOS
Ultrasound in pregnancy | PHOTO
Ultrasound in pregnancy | Examples of ultrasound scans during the 40 weeks of pregnancy
Before carrying out the exam it will be necessary, through aechography, establish the exact position of the placenta from which to take the sample useful for analysis. The villocentesis is able to highlight chromosomal abnormalities linked to numerous diseases, in particular:
- trisomy 21 (Down syndrome),
- trisomy 18,
- sexual chromosomal aneuploidies;
- muscular dystrophy of Duchenne and Beker
- cystic fibrosis
When should the CVS be done
The villocentesis must be done by tenth to thirteenth week of pregnancy. This examination is not mandatory and is recommended by the doctor in the following cases:
- if the mother is over 35;
- if there is a family history of chromosomal abnormalities;
- who have had children with macrosomal abnormalities;
- if the prenatal screening gave a positive result;
- in case of positive result of the combined test (bi-test and nuchal transulence),
- if one or both parents are healthy carriers of genetic diseases.
Risks of CVS
La villocentesis it's an exam invasive so it may involve a risk, albeit minimal, with an inauspicious outcome. In particular, chorionic villus sampling presents a risk of spontaneous abortion up to 1%, while there is a 0,5% risk of unclear results requiring re-examination, if for example too small a sample has been taken that does not allow accurate analysis.
Is CVS painful?
CVS is an invasive examination for both the mother and the fetus: it involves the insertion of a August at the abdominal level, in the area under the navel, so it can certainly be annoying. Many women declare that they have felt nothing but a kind of strong aspiration in the area where the sample is taken, others declare that they have felt a slight pain. However, it is a nuisance limited to a few minutes and certainly bearable.
Villocentesis and rest
After the exam is required bed rest for the next day and in general attention and rest for a couple of days. In particular, women are asked to avoid any physical activity in them 48 hours later on examination.
In case of abdominal pain, uterine contractions, bleeding or fever it is important to go to the emergency room or call your gynecologist.Read also: Amniotic fluid, the first protection
Cost of the villocentesis
CVS can be done in private settings and the cost varies between 500 and 1200 euros, depending on the type of analysis to be done on the sample. It is important to rely on specialized centers and operators of undoubted experience because the villocentesis remains a particularly complex technique, given the small size of the area in which the chorionic villus sampling is taken.
The new Essential Levels of Care have included CVS and amniocentesis in the list of services for free in pregnancy but only if previous screenings have given positive results. So you must first undergo the combined test:
- bi-test: blood analysis;
- nuchal transulcence: a particular ultrasound that measures the thickness of the fluid that is between the skin of the nape of the fetus and the underlying membranes at the level of the neck and offers a calculation of the probability that the child has a chromosomal abnormality.
If, then, this screening methods should it give a positive result, the future mother will be referred to a center that carries out villocentesis or amniocentesis and this examination will be borne by the National Health Service.
Results of the CVS
After chorionic villus sampling the sample is sent to the laboratory to be analyzed. As we read on the NHS, the number of chromosomes and their structure are counted in order to highlight anomalies. If the CVS is performed for a specific genetic disease, the test can be more accurate and analyze the cells in search of this pathology.
Results are typically available within few days if it is a question of highlighting Down Syndrome, while it may take longer to analyze rarer genetic conditions.
Reliability of CVS
It is estimated that theaccuracy of the villocentesi is attested on 99%. However, it is good to know that a defect that occurs only after birth cannot be excluded, so it can never be said that it is a conclusive and definitive result.
If the results are normal it means that none of the genetic diseases analyzed have been found, however a normal result cannot guarantee that the child will be completely and surely healthy. THE genes have been identified. there are many, as well as and possible chromosomal abnormalities, and therefore the possibility that there is a genetic defect not detectable with the prenatal test done during pregnancy cannot be excluded.
If the sample collected is insufficient for an accurate analysis, the woman may have to undergo a new withdrawal, but there are also some cases where amniocentesis that is performed later in the weeks of pregnancy is more accurate.
In case of "positive result”Means that a genetic anomaly has emerged which will be clearly indicated in the documents. It will be up to you to decide what to do in this case: you can consult a geneticist to understand the true extent of the defect found and make an informed choice. Before making a decision it is important to have a clear picture of the genetic disease that interests the child: are there any treatment options? What problems does it entail? What life expectancy is there?
Villocentesis or amniocentesis
Both are techniques aimed at making one prenatal diagnosis of genetic diseases and chromosomal abnormalities. L'amniocentesis it is performed at a later stage of pregnancy, between 15th and 18th week gestation, while the villocentesis is done well before. Perhaps for this reason it has always been believed that villocentesis involves greater risks. In fact, more accurate studies have shown that the risk of miscarriage it is almost the same for amniocentesis and villocentesis.
The fact remains that CVS is certainly one more procedure complicated to be performed, because it is necessary to take the chorionic villi in a very precise area of the placenta, however it allows, in the event of a positive result and if you choose to terminate the pregnancy, to be able to do a curettage instead of a real therapeutic abortion.