The chorionic villus test is a genetic test performed in pregnancy to detect biochemical and DNA abnormalities in the fetus, such as Down syndrome, cystic fibrosis and others. It involves taking a test sample from the placenta and analyzing it in the laboratory. It is one of the most accurate diagnostic tests. Find out when to do it and what you need to know about this test!
When is this test recommended?
The chorionic villus or CVS test is generally recommended for pregnant women who:
presents with increased risk of Down syndrome;
presents risk of other chromosomal abnormalities;
pregnant women over 35;
mothers who have already given birth to a child with Down syndrome;
pregnant women with close relatives who have genetic diseases.
How is the test done?
The test involves several procedures. It is important to know that you have to have a full bladder before it is done, because part of the procedure also involves ultrasound ultrasound.
During the test you will be stretched. You will have an ultrasound so that the doctor can find out how many weeks it is the task and to locate the placenta.
Depending on the stage of pregnancy you are in, the placement of the placenta and personal preference, the doctor will choose one of the following methods to take the tissue sample:
transvaginal sampling (it is done between 11 and 13 weeks, the sampling takes place through the cervix);
transabdominal sampling (after 13 weeks, it is done by inserting a needle through the abdomen, and uterus to the placenta, but you will be anesthetized locally during the procedure).
In either of these methods, the doctor will use ultrasound at the same time to guide the needle to take the chorionic villus fragment from the placenta.
Many pregnant women feel rather uncomfortable during the procedure and sometimes show small periods when they have pain, but they can bear it. They pass pretty quickly. The test does not last more than half an hour in total.
Are there side effects of the test?
You can experience:
moderate or severe abdominal pain or cramps;
leakage of amniotic fluid through the vagina;
redness and local inflammation (where the needle was inserted) etc.
What can be found after the chorionic villus test?
detects congenital chromosomal abnormalities;
detect genetic problems that could be inherited from the family (hemophilia, Tay-Sachs disease, cystic fibrosis, thalassemia), especially if you have a family history of such anomalies;
establishes the child's gender, especially if there are indications that he or she may be suffering from a genetic disorder related to sex;
establishes the blood group of the fetus especially if there has been a sensitization of Rh factor.
Why chorionic villus test and not amniocentesis?
Both tests are performed for the same purpose, so you might be wondering why you would use the CVS test instead of classical amniocentesis. Doctors argue that the chorionic villus test can be done much earlier (in weeks 10-13) while amniocentesis cannot be performed faster than 15 weeks.
So, if you want to know much earlier in the pregnancy whether or not your baby is suffering from congenital abnormalities, this test is an effective solution.
Is there a risk that the fetus will be affected during the procedure?
Unfortunately, there is a higher risk than in the case of amniocentesis to lose pregnancy, but with a little higher. If the risk of pregnancy loss in the case of amniocentesis is 1%, in the case of CVS test it is 2%.
There are other risks associated with this test, but they only occur if the procedure takes place at a young age of pregnancy. If this is done before 10 weeks there is a risk that the fetus will be born with limb defects, but the risk is small.
Also, if you are infected with HIV, there is a risk that during the procedure the virus will be transmitted to the fetus, which is not valid in the case of hepatitis B or C.
When do you get the results?
It usually takes quite a long time until you get the test result, around 14 or 21 days. The tissue taken is taken to the laboratory and subjected to careful procedures regarding the complete counting and examination of the chromosomes.
Tags Medical analysis during pregnancy Amniocentesis