Chorionic villus sampling (cvs)
How is Chorionic villus sampling (cvs)performed?
What is chorionic villus sampling?
When an early diagnostic test is needed, chorionic villus sampling serves the same purpose as amniocentesis but can be performed earlier in the pregnancy.
Also known as a chorionic villus biopsy, this procedure consists in removing very small fragments of the placenta called chorionic villi. It is performed between 11 and 14 weeks of pregnancy, if there is a risk of birth defect such as increased nuchal translucency or cystic fibrosis because one of the parents carries the gene.
The sample is removed using a very thin needle attached to a syringe. Using ultrasound guidance, this needle is inserted through the mother’s abdominal wall to reach the placenta. CVS is performed by a doctor specialized in fetal medicine who will accompany you throughout the procedure.
The procedure can be slightly painful, which is why local anesthesia at the injection site is used.
During a chorionic villus biopsy, the fetus does not feel anything and the extreme precision offered by ultrasound guidance means the doctor can remain at a safe distance from the baby at all times.
What is the purpose of chorionic villus sampling?
The cells collected will be analyzed in a specialized laboratory accredited by the French Biomedicine Agency
This analysis is used to:
- Perform a fetal karyotype (photographic representation of the fetal chromosomes) in order to search for chromosomal abnormalities;
- Search for genetic abnormalities, such as the abnormality which causes cystic fibrosis or fragile X syndrome (a genetic disease causing intellectual disability).
However, this procedure does not detect all potential diseases.
When should chorionic villus sampling be performed?
CVS is usually done before three months of pregnancy, 11 to 14 weeks after the last menstrual period.
You will systematically be asked to undergo CVS if you are on medication (aspirin, anticoagulants) and if you have allergies (iodine, local anesthesia).
Does cvs carry risks for the fetus?
CVS is performed under optimal safety conditions, including the use of sterile material by specifically trained staff. However, there are risks, namely: possible miscarriage or premature birth (0.1% of cases), especially eight to ten days following the procedure; very rare cases of premature rupture of the membranes or infection of the amniotic fluid.
What should you expect afterwards?
After the procedure, you will be given an antispasmodic medication. A blood test may be performed to make sure the cell sample has not been contaminated by your blood. We recommend that you rest for 48 hours afterwards and take pain killers if necessary. You will be placed on sick leave and receive a prescription for pain killers.
For a few hours, you might feel cramping or pain where the needle was introduced. This is normal and no cause for concern.
Please note: If your blood is Rh negative and your fetus’s is Rh positive or undetermined, we will prescribe a 300 mcg injection of Rophylac® to be used as a prophylaxis against alloimmunization.
Results may be obtained in two separate phases, depending on the type of analyses performed:
- When screening for chromosomal abnormalities, data on trisomy 21, 18 and 13 are available within two to three days.
- The complete karyotype analysis can take two to three weeks because it requires a cell culture (multiplication of cells in a nutrient-enriched medium). Results may be delayed if the cells take longer to develop.
In rare cases, the cell culture is unsuccessful, making it necessary to discuss the possibility of a second CVS procedure.
You must go to an emergency service specializing in gynecology near your home or contact the 24/7 emergency department of the American Hospital of Paris at +33 1 46 41 25 25 if you experience any of the following after the procedure:
- Loss of amniotic fluid
- Contraction-like pain