Information About Chorionic Villus Sampling (CVS) Test

Submitted on March 27, 2012

What is Chorionic Villus Sampling (CVS)?

Chorionic villus sampling or CVS is a prenatal test that can help to identify problems with the baby in the fetal stage. The test is usually performed during the tenth to twelfth week of pregnancy.

A CVS is a diagnostic test that is normally done to identify birth defects such as Down syndrome. It is also done to identify problems such as Tay-Sachs disease, sickle cell disease, cystic fibrosis, or thalassemia, all of which are basically genetic in nature. Further, a CVS can help to identify the sex of the baby if the mother has a sex-linked disorder like hemophilia.

A chorionic villi sampling procedure involves a biopsy of the chorionic villus cells that are found in the placenta. These cells are similar to the baby's cells, thus helping a doctor in identifying a condition in the prenatal state.

Chorionic villus sampling procedure. The doctor will ask the patient to be prepared with a full bladder before the test. The bladder can be filled by drinking water at least an hour before the test and avoiding urination after drinking water. A specialist called the perinatologist conducts the procedure. The sampling procedure is either done through the belly or through the cervix. If the procedure is done through the belly, it is termed a transabdominal CVS, and if it is done through the cervix, it is called a transcervical CVS.

Transabdominal CVS

This procedure is done through the belly. The procedure begins with an ultrasonography, which can help to identify the position of the baby, the placenta, and the heart beat. Once the position has been identified, the doctor inserts a long thin needle into the placenta from the belly to collect the sample. The patient may feel a stinging sensation during the transabdominal CVS, and in some cases, the doctor may chose to administer anesthesia.

Transcervical CVS

This procedure is done through the cervix. The patient is first asked to lie back with her legs supported on stirrups. The vaginal walls are then opened with a speculum. This helps the doctor to see the cervix. Once the cervix is visible, a catheter is guided to the placenta through the cervix. An ultrasonography is used to view the path of the catheter. Once it is at the right location a sample is collected for further analysis. This procedure is normally painless and feels very similar to a cervical pap smear test.

Interpretation of Test Results

The results of a CVS test can either be normal or abnormal. A normal result indicates that there are no genetic or chromosomal abnormalities with the baby. There are a few risks associated with the CVS procedure such as leakage of the amniotic fluid and vaginal spotting, which tend to go away in a couple of days. It is also important to know that CVS can increase the risk of having a uterine infection. It also carries the risk of a miscarriage, albeit very low.