Chorionic villus sampling (CVS) is a test to examine the fetus for chromosomal abnormalities. This pamphlet explains who the test is offered to, how it is carried out and what it looks for. You can also read about the procedure related risks of CVS, and how you will receive the results.

Who will be offered CVS?

• Pregnant women where the likelihood of the fetus having Down’s syndrome (trisomy 21) is greater than 1:300 or if the risk of trisomy 18 or trisomy 13 is greater than 1:150.
• Pregnant women who have an increased risk of chromosomal abnormalities in the fetus
• Pregnant women where an abnormality has been detected in the fetus by an ultrasound scan which may be due to chromosome abnormalities.

When is CVS carried out?

CVS is carried out after 10 weeks of pregnancy (10 weeks + 0 days). In rare cases, the location of the placenta will make it impossible to perform a sample. In these cases, the test will be postponed, or changed to an amniocentesis instead. Amniocentesis can be performed after 16 weeks of pregnancy (16 weeks + 0 days).

How is a CVS performed?

First an ultrasound will be carried out to check the location of the placenta in the uterus. The skin will then be washed with disinfectant liquid. A thin needle will be inserted through the abdominal wall. A local anaesthetic is not used. The test will take 10-15 minutes. We recommend that you rest afterwards for about 20 minutes before going home. Take it easy the rest of the day.

What should I be aware of?

You can go to work the next day unless you have a physically demanding job. If this is the case, you should take the next day off.

You may feel some discomfort after the procedure such as muscle soreness, period-like cramping and a downward pull in your abdomen.

The discomfort often disappears within 24 hours and does not require treatment. If needed, you can take a 1g paracetamol tablet, available over-the-counter (always read the patient information leaflet). Some women experience spot bleeding.

NOTE: Contact a doctor if you begin bleeding heavily, if amniotic fluid begins to leak, or if you experience strong pains. You can contact the Ultrasound Clinic during our telephone hours. Outside these hours, dial 1813.

Risks in connection with CVS

The risk of miscarrying after CVS is approximately 0.5%. Most miscarriages that happen after CVS will occur within 1-2 weeks.

What can a CVS detect?

CVS can be used to diagnose chromosomal abnormalities in the fetus. The most well-known is Down’s syndrome.

CVS does not a guarantee a healthy and normal child since it cannot diagnose all chromosomal abnormalities or genetic diseases.

Getting the results

The sample will be sent to the Chromosome Laboratory at Rigshospitalet. The sample will be thoroughly analysed using micro-array.

The analysis will take about 10 working days. If the results are normal, you will receive the results in your E-boks as soon as they are available. If the results are not normal, you will be contacted by telephone.

Further information about CVS

If you would like to know more about CVS, you can call The Ultrasound Clinic to book an appointment.