Complications of chorionic villus sampling 

Before you decide to have chorionic villus sampling (CVS), your GP, midwife or genetic counsellor will discuss the risks and possible complications with you.


CVS carries a risk of miscarriage, which is when the pregnancy is lost in the first 23 weeks.

The risk of miscarriage after CVS is estimated to be about 1-2%, although it is difficult to determine which miscarriages would have happened anyway and which are the result of the CVS procedure.

In most cases, miscarriages linked to CVS occur within two weeks of the procedure.

It is thought that the risk of miscarriage after CVS may be slightly higher than after an alternative test called amniocentesis.

Inadequate sample

In less than 1% of procedures, the sample of cells that is removed may not be suitable for testing. This could be because not enough cells were taken, or the sample was contaminated with cells from the mother.

If the sample is unsuitable, it may be necessary for the CVS procedure to be carried out again.


As with all types of surgical procedures, there is a risk of infection during or after CVS. Infection can occur if there are bacteria on your skin or on the instruments being used.

However, severe infection occurs in less than one in every 1,000 procedures.

Rhesus sensitisation

If your blood type is rhesus (RhD) negative but your baby’s blood type is RhD positive, it is possible for sensitisation to occur during CVS. Rhesus sensitisation is where some of your baby’s blood enters your bloodstream and your body starts to produce antibodies to attack it.

If it is not treated, this can cause rhesus disease in the baby. An injection of a medication called anti-D immunoglobulin is now widely used to prevent sensitisation occurring.

Read more about preventing rhesus disease.

Page last reviewed: 14/10/2013

Next review due: 14/10/2015