Pregnancy & prenatal testing: First trimester

Most pregnancies produce healthy babies however, in some cases there is a risk of a baby having a birth defect caused by a genetic abnormality. In this situation chorionic villus sampling may be discussed.

Chorionic villus sampling (CVS) is normally performed between the tenth and twelfth week after a woman’s last menstrual period. The test involves taking a sample of 'chorionic villi’, which are found in the placenta, using a needle passed into the mother’s womb. The placenta has the same genetic make-up (DNA) as the baby, and so the sample can be used to look for genetic abnormalities in the baby’s DNA.

Complications associated with CVS
There is a risk of miscarriage (approximately 1%) associated with the CVS procedure. An infection may develop.

Limitation of testing
Not all genetic disorders can be detected.