Chorion Villus Sampling 11-14 weeks
CVS involves the examination of chorionic villi (placental tissue). Both the baby and placenta (afterbirth) develop from the same cell therefore the chromosomes present in the cells of the placenta are the same as those of the baby.
A local anaesthetic is given. A fine needle is then passed through the abdomen and a sample of villi is taken. The procedure lasts 1-2 minutes and is performed under scan guidance. CVS is not performed before 11 weeks.
Many women find the procedure uncomfortable rather than painful, and describe feeling period-type pains. However, it’s over relatively quickly. The test lasts no longer than half an hour from start to finish and actually taking the sample is only a matter of a few minutes
The results for Down’s syndrome and other major chromosomal defects are usually available within 3 days. The results for rare defects take 2 weeks.
The main advantage of CVS over amniocentesis is that it can be performed earlier; usually between 11 and 14 weeks of pregnancy, compared to amniocentesis which is recommended from 16 weeks of pregnancy (RCOG 2005).
Risks
The risk of miscarriage due to CVS and Amniocentesis is about 1% In approximately 1:1000 cases the test will need to be repeated because the results are inconclusive. If you were to miscarry due to the test, this would happen within the next five days. Some studies have shown that when CVS is performed before 10 weeks there is a small risk of abnormality in the baby’s fingers and/or toes. To avoid this risk we never perform CVS before 11 weeks.
If we suspect there is a problem with your baby, we can refer you to an expert who specialises in performing CVS (Chorion Villus Sampling).
