Chorionic Villus Sampling (CVS) Test During Pregnancy

Scientific development has made it possible to detect adverse health conditions in a baby even before birth. There are a range of tests which are carried out at the time of pregnancy in order to determine if the baby is suffering from any diseases or medical condition. Early detection of an adverse medical condition in the baby can allow the doctors to take necessary corrective measures in order to ensure that the baby is born healthy and free of life-threatening conditions.

What is Chorionic Villus Sampling Test?

Chorionic villus sampling test is an antenatal test which is performed to diagnose if the baby has a particular genetic disorder such as the Down’s syndrome or inherited conditions such as thalassaemia and sickle cell anaemia. Chorionic villi are tiny, finger-shaped growths found in placenta, which have the same genetic material as the baby’s cells. The CVS pregnancy test is performed during early pregnancy, usually between the 10^th and 13^th weeks.

Is CVS Test Applicable to All Pregnant Women?

CVS prenatal test is not a routine test and is offered to be performed under the following conditions:

• Abnormal results from a prenatal screening test: If the first-trimester screening result is positive or abnormal, the doctor might recommend getting a CVS done in order to ensure the length of a medical problem in the baby.
• A chromosomal abnormality in a past pregnancy: If you have experienced chromosomal abnormality in a past pregnancy, or have a child with Down’s syndrome, you will be offered this test.
• Family medical history point towards increased health risk: CVS testing might be recommended if there is a family history of a genetic disorder.

CVS is not recommended to women who have an active sexually transmitted infection, are carrying twins or have experienced vaginal bleeding during pregnancy.

How to Prepare for the Test

Your health care provider will explain the entire procedure of the test in details and ask you to sign a consent form before initiating the procedure. The health care provider will use ultrasound to determine the position of the baby and that of the placenta. Drink lots of water leading to the test as the ultrasound will require a full bladder.

How is the CVS Test Performed

The CVS early pregnancy test is performed by taking a sample of cells, called ‘chorionic villi cells’ from the pregnant woman’s placenta. The sample of cells might be taken from the abdomen or from the cervix.

• Sample Taken From Your Abdomen

A long, thin needle is inserted through the abdominal wall into the uterus and a tissue sample will be withdrawn from the placenta into a syringe. The needle does not enter the amniotic sac or go near the baby and the procedure is performed under local anaesthesia.

• Sample Taken Through the Cervix

A thin, hollow tube is inserted into the cervix through the vagina. When the catheter reaches the placenta, gentle suction will be used to remove a tissue sample.

• After the Procedure

The procedure takes around 10 minutes to perform. Once the test is complete, you will be monitored for an hour in case any side effects, such as heavy bleeding, surface and need immediate attention. Once the formalities are complete, you can go home and rest.

Is the CVS Test Painful?

CVS test is usually described as uncomfortable rather than painful. You might experience stinging sensation and cramps during and after the test has been performed and may have a sore tummy afterwards. Usually, local anaesthesia will be administered before performing the test in the area where the needle is inserted.

What is the Right Time for Performing Chorionic Villus Sampling(CVS) Test?

CVS testing is to be performed between 10^th and 13^th week of pregnancy. In some circumstances, the testing might be carried out at a later stage of pregnancy. However, the test should not be carried out prior to the 10^th week as the risk of CVS causing complications, such as birth defects or miscarriages is higher during this period.

When Do You Get the CVS Test Result

Post CVS testing, two types of laboratory tests are performed on the samples taken from the placenta. The first result is available within a few days, and tells if there is any major chromosome problem. The full results, highlighting the smaller, rarer conditions can take two to three weeks. If the test has been performed to identify a specific disorder, then the results might take up to a month.

Problems That Can Be Faced After the Test

CVS testing involves the use of needles and suction tubes entering the body and this might lead to side effects post the procedure is completed. Following are some of the problems that can surface after the test:

• Persistent and severe pain
• High temperature
• Shivering or chills
• Heavy vaginal bleeding
• Contractions and cramps
• Discharge of clear fluid from vagina
• Infection and spotting

Possible Risks Involved with CVS

CVS testing is an invasive procedure which comes with several risks. It is important to weigh the risks vis-à-vis the benefits before agreeing to get the CVS procedure done. Following are some of the common risks of getting the test done:

1. Bleeding and cramping:

The test procedure can cause heavy vaginal bleeding or spotting and cramps which are similar to menstrual cramps.

2. Infection:

You may experience uterine infection after the test. Although the situation is rare.

3. Rh Sensitization:

CVS testing can cause a small amount of your baby’s blood to enter your bloodstream which may cause complications such as Rh sensitization, especially if you are Rh – negative.

4. Accidental Abortion or Miscarriage:

CVS testing can also lead to the risk of an accidental abortion or miscarriage. The risk of miscarriage on performing CVS is in addition to the miscarriage risk which all women face in early pregnancy due to natural causes. One or two in every hundred women that opt for CVS testing experience miscarriage.

5. Foetal Limb Deformities:

CVS test may also cause your baby to have missing toes or fingers. However, this risk usually exists in cases where the testing is done before the 10^th week of pregnancy.

What Does CVS Pregnancy Test Result Mean?

The CVS test results are estimated to be 99% accurate with very less margin for errors. While CVS can be used to test specific genetic disorders, it cannot test for every birth defect. The CVS pregnancy will either be normal (i.e. negative) or abnormal (i.e. positive).

1. Normal Results:

When the test results do not show any defect or deficiency, the report is a normal or a negative report. Although the report might not show any defects, it is possible that the child might be born with the condition that was tested for or with another genetic condition.

2. Abnormal Results:

If the report shows ‘positive’ results, your baby has a condition which was being tested for. There is no cure for most chromosomal conditions and hence, the implications for such disorder will be fully discussed with you.

What to do if the CVS Test Shows an Abnormality?

The implications of an abnormal result will be discussed with you and the possible remedial options will be shared. Since most genetic conditions cannot be treated, you may have the following options:

• To continue with the pregnancy and be prepared for taking necessary care of your baby post birth
• To terminate your pregnancy, in which case you will have to discuss with the doctor about the advisability of doing so

What are the Alternatives for CVS Test?

Amniocentesis is an alternative for CVS test wherein a sample of mother’s amniotic fluid is taken for testing. Amniocentesis is carried out between 15^th to 20^th weeks of pregnancy. The advantage of CVS testing is that it is performed at an early stage of pregnancy unlike amniocentesis which is done at the advanced stage of pregnancy.

Things to Consider

Before deciding to get the test done, it is important to consider the risks associated with the test and the outcome which is expected. An individual or a couple should assess and discuss the benefits of the testing thoroughly with your doctor and understand the possible risks clearly.

Taking a well-considered decision about whether a CVS test is required for the successful continuation of the pregnancy will help you take all the necessary precautions.