What Is Chorionic Villus Sampling?

Chorionic villus sampling, known as CVS, is a medical procedure that can allow for the prenatal diagnosis of various genetic disorders. It involves the removal of a small sample of placental tissue (chorionic villi) which is then sent to a laboratory for analysis. It can be used to test for conditions such as Down syndrome, cystic fibrosis or other genetic disorders for couples at risk.

CVS is usually performed after 10 weeks. It can be done either by passing a catheter through the cervix into the placental tissue, or by passing a thin needle through a woman’s abdomen and uterus and into the placenta. Both techniques are done with the help of ultrasound guidance. In the case of twins or more, each placenta is sampled separately.

The advantage to CVS over amniocentesis, in which amniotic fluid is withdrawn at about 15 to 18 weeks, is that an earlier diagnosis can be made. Transabdominal CVS has similar risks of miscarriage as amniocentesis, and those risks are relatively low, and may vary based on the experience of the physician performing the procedure.

Many years ago there was a concern raised about defects of the limbs with CVS. However, there does not seem to be a significant risk of limb defects when CVS is performed at 10 weeks or later.

If you are considering CVS, you should meet with a genetic counselor first to discuss your family history (as well as your partner's or sperm donor’s history) and also discuss the risks and benefits of the procedure. Recently, there have been several additional tests, such as microdeletion panel or microarray which can test for additional disorders beyond just the standard chromosomal analysis.