The chorionic villus sampling (CVS) is a diagnostic invasive method for detecting chromosomal abnormalities i.e. Down’s syndrome and some other chromosomal or genetic syndromes. During this examination, we take a sample from the placenta. The fetus and the placenta originate from the same cells, so the chromosomes of the placenta cells are the same with those of the fetus.
How is CVS conducted?
Initially, we give local anaesthetic and a thin needle is inserted through the abdomen of the mother to the placenta. The examination is conducted under continuous ultrasound guidance and lasts about 1 minute.
What should I expect after the CVS?
For the first two days after the CVS, you may feel some pain in the abdomen, like period pain, or you may have vaginal bleeding. These are the most common symptoms and usually the pregnancy continues without any problems.
When am I going to receive the results?
The results for Down’s syndrome and other serious chromosomal abnormalities are available within 3 days. The results for rarer chromosomal abnormalities are usually available within 2 weeks.
Does the test need to be repeated?
In 1% of the cases that the results are dubious due to placental mocaicism, an invasive test later in pregnancy (amniocentesis) needs to be repeated.
What are the risks associated with CVS?
The risk of miscarriage due to CVS is 0.5-1% and is the same as the risk from amniocentesis which is conducted after 16 weeks of pregnancy. Miscarriage is due to an accident during the test and therefore if we are happy with the process and listen to the fetal heart rate immediately after the CVS, we are relieved that everything went well. In any case, if you are to miscarry due to the procedure, this will happen within the next 5 days.
In some studies, it is shown that if CVS is performed before 10 weeks of pregnancy, there is a minor risk of abnormalities of the fetal fingers and toes. That is the reason why CVS is never conducted before 11 weeks of pregnancy.