Chorionic villus sampling (CVS)

Chorionic villus sampling (CVS) is a prenatal test in which a sample of chorionic villi is removed from the placenta for testing.

CVS isn't routinely offered to all pregnant women. It's only offered if there's a high risk the baby could have a genetic or chromosomal condition.

CVS is usually carried out between the 11th and 14th weeks of pregnancy.

There are two methods of CVS: transabdominal CVS and transcervical CVS. You only need to learn one.

Transabdominal is the most common method used.

The abdomen is cleaned using an antiseptic wipe.

Using an ultrasound image to locate the foetus a very fine needle is inserted through the skin into the womb into the placenta. 

A syringe is attached to the needle and is used to extract a small sample of cells from the chorionic villi. The needle is then removed and the sample is sent away for analysis.

The test takes around 10 minutes, although the consultation may take 30 minutes.

The procedure is usually described as being uncomfortable rather than painful, although they may experience some cramps that are similar to period pains for a day or two.

The sample is analysed in a lab and the number of chromosomes are counted and/or examined. They are looking for faulty genes.

Positive result - baby has a disease thats being tested for:

• CF - the CTFR gene on chromosome 7 doesn't work properly
• Muscular dystrophy - Faulty gene means a protein called dystrophin cannot be made in the muscles.
• Sickle cell anaemia - Genes are faulty and affect the ability of the body to make haemoglobin.

Negative result - no abnormalities detected.