Chorionic villus sampling or CVS is a procedure in which a sample of chorionic villi is removed from the placenta for testing. During pregnancy, the placenta provides oxygen and nutrients to the growing baby and removes waste products from the baby's blood. The chorionic villi are wispy projections that make up most of the placenta and share the baby's genetic makeup.
Before the procedure, your health care provider will use fetal ultrasound to show your baby's position on a monitor. If the placenta is in a favorable position, your health care provider might take the sample through your cervix. Your health care provider will open your vagina with the speculum and insert a thin, hollow tube, called a catheter, through your cervix.
When the catheter reaches the placenta, gentle suction will be used to remove a small tissue sample. This is known as a transcervical chorionic villus sampling. If the placenta isn't clearly accessible through the cervix or you have a cervical infection, your health care provider might take the sample through your abdominal wall.
Guided by ultrasound, your health care provider will insert a long, thin needle through your abdominal wall and into your uterus. The tissue sample from the placenta will be withdrawn into a syringe, and the needle will be removed. This is known as a transabdominal chorionic villus sampling. The small amount of tissue that's removed will be replaced naturally.