CVS or the test of chorionic villi is carried out by way of taking a small piece of the chorion, i.e. the developing placenta.
Chorionic villus sampling (CVS) is usually performed to analyse the chromosomes of the foetus to identify various chromosome disorders before birth.
You will be assigned to a CVS when the previous tests (nuchal translucency test, double test, triple test) have indicated the possibility of chromosome disorders or there are indications of chromosome disorders in your medical history.
CVS is optional and you have the final say whether you want this test. Before the test you must sign an instrument of agreement.
How is CVS performed?
In the case of CVS, the cells of the placenta are analysed. The chromosomes of the cells found in the chorion are similar to the ones of the foetus. The foetus is located in the amniotic cavity, suspended in amniotic fluid, surrounded by the chorion. In order to inspect the cells, a small tissue sample is taken from the chorion with a thin needle through the belly during ultrasound. The cells from the tissue are suspended in a special nutrient solution to grow for a while, and then the multiplying cells can be inspected under a microscope. The final results of the analysis arrive after one or two weeks.
When is the optimal time for CVS?
CVS is usually performed on the 12th week of pregnancy, but it can also be performed later. It is considered safest during the 12th to 13th week.
Does the procedure hurt?
The procedure may feel uncomfortable, but most women don’t find it more painful than taking a blood test from the vein. Before the procedure the belly is numbed using a special ointment, similar to the one used in dentistry. If you are allergic to the ointment, you must notify the doctor beforehand. After the procedure some bleeding might occur and you may feel a slight sensation of distention in the stomach, which is normal. If the bleeding is increasing, consult with a doctor.
What are the risks of CVS?
CVS is a relatively common procedure with rare complications. For most women, the information obtained as a result of the test overrides the risk involved in the procedure.
- The risk of miscarriage is increased by approximately 1-2% with CVS. The exact reason for this is unknown. Most of the pregnancies continue without issues.
- An aseptic (sterile) method is used for the test to avoid infections, but nevertheless inflammations may occur on rare occasions in the form of fever, contractions of the uterus and stomach pains.
- Rhesus negative women (RhDˉ) have an increased risk of blood cells of the foetus transferring to the blood circulation of the pregnant woman, leading her to develop antibodies. To reduce this risk, an antibody injection is done if necessary, which reduces the risk of immunization against the foetus.
Results of CVS
The results of CVS arrive in one to two weeks after the procedure. At first you are notified of the results via telephone and after a few days, the written results reach your gynaecologist or midwife. The results give information about the tested disorders. If the results indicate that the foetus has a genetic disease, the results and further steps are explained to you. According to Estonian law, the termination of pregnancy on medical grounds is allowed for up to 21 weeks of pregnancy. If you decide to abort the pregnancy, you will need to turn to a doctor or a midwife for additional information.
What to note?
If you have strong stomach pains, bleeding, extensive discharge or a fever after the test, you should immediately turn to a doctor on duty at the emergency room of the women’s clinic.