When you think about the baby you are expecting, you probably feel both excited and a little scared, right? It is normal to wonder if the baby will be healthy or if there will be any problems. So, today we are going to talk about a special test that is done during pregnancy to check if the baby has any genetic problems or birth defects. This is called the Chorionic villus sampling , or CVS for short.
Simply put, what is CVS?
Simply put, CVS is a test that is performed early in pregnancy to detect genetic diseases, chromosomal problems, and other birth defects in the unborn baby. It involves taking a very small sample of cells from the area where the placenta attaches to the uterine wall.
We call these cells chorionic villi. Since they are formed from the fertilized egg itself, these cells contain the baby's genes . This means that by examining these cells, we can get a clear idea of the baby's genetic information.
Why is this CVS test recommended?
This test is not usually recommended for everyone. If your doctor thinks you have a risk factor, such as a higher chance of having a child with a genetic disease or birth defect, he or she may recommend this test.
One of the biggest advantages of this is that it can tell you for sure if there is a problem very early in your pregnancy. Especially if you are expecting twins, the results of regular blood tests are not very accurate. In such cases, a CVS test can provide a clear answer. However, the risks of having a CVS test for a pregnant mother with twins are slightly higher.
What diseases can and cannot be detected by CVS?
There are several major medical conditions that this test can detect. And there are also things it can't detect. Let's take a look at what they are.
| Recognizable situations | Unrecognizable situations |
|---|---|
| Chromosomal abnormalities such as Down syndrome. | Open neural tube defects, such as spina bifida. |
| Genetic diseases such as cystic fibrosis, Tay-Sachs disease, and sickle cell anemia. | (Other tests are needed to diagnose such conditions.) |
| Because the sex of the child can be determined, diseases that are specific to only one sex (e.g., certain muscular dystrophies that are more common in boys) can be identified. |
This test is considered to be about 98% accurate in detecting chromosomal defects, meaning it is a very reliable test.
What are the benefits of CVS testing?
The biggest advantage of this is that it can be done early in pregnancy (usually between 10-12 weeks). It can be done earlier than another test called amniocentesis. The results can usually be obtained within 10 days.
Receiving this kind of information early in pregnancy is a great help for parents in making future decisions.
Imagine, if a couple decides to terminate a pregnancy after receiving some adverse results, it would be safer for the mother's health to implement that decision early on rather than waiting for the amniocentesis results to come in and then doing so later.
Are there any risks involved in this test?
Yes, as with any medical test, there are some risks. Because this test is performed early in pregnancy, the risk of miscarriage may be slightly higher than with amniocentesis. There is also a risk of infection.
In very rare cases, especially if this test is done before 9 weeks, there have been reports of defects in the baby's fingers. For this reason, this test is usually not done until 10 weeks .
The most important thing is to discuss these risks with your doctor before having this test. Especially if you are having twins, make sure you have a doctor who is experienced in this test.
Who is the CVS test recommended for?
Doctors generally recommend that mothers with the following risk factors consider this test:
- Mothers aged 35 or over (the risk of having a child with a chromosomal defect such as Down syndrome increases with age).
- Couples who already have a child with a birth defect or who have a family history of such a condition.
- If one of the parents has a known chromosomal abnormality or genetic disease.
- Mothers who received abnormal results from other genetic tests performed during pregnancy.
Your doctor can give you the best advice on whether this test is right for you. But ultimately, the decision to have this test or not should be made by you and your partner, after a thorough discussion with your doctor.
How is the CVS test performed?
Before undergoing this test, you and your partner will be referred for genetic counseling, where the benefits, disadvantages, and risks of this test will be clearly explained to you.
An ultrasound scan is then performed to check the gestational age of the baby and the exact location of the placenta. The test is done later, usually between 10 and 12 weeks after your last menstrual period.
There are two main methods for obtaining a cell sample from the placenta.
Through the vagina (Transvaginal method)
In this, a device called a speculum is inserted into the vagina, similar to a Pap test. Then, a very thin plastic tube is inserted through the vagina and up the cervix. Under the guidance of an ultrasound scan, this tube is guided to the placenta, where a small sample of cells is scraped from there.
Through the abdomen (Transabdominal method)
In this method, similar to an amniocentesis test, a very thin needle is inserted through the abdomen and passed into the placenta. A sample of cells is then taken from there.
The cell sample obtained this way is sent to a laboratory. There, the cells are grown in a special liquid and tested over a few days. Full results can be obtained within 2 weeks. Your doctor will inform you of the results.
Is this a painful test?
You may feel some pain, but it will pass quickly . The entire test will take a maximum of 30 minutes from start to finish. It only takes a few minutes to collect the sample.
What happens after the test?
You will need to rest for a while after the test. So it is a good idea to bring someone home with you. You should rest for the day. You are usually advised to avoid heavy lifting, exercise, and sexual intercourse for 3 days.
You may experience some cramping and light bleeding, which is normal. But let your doctor know about it. Most importantly, if you notice any watery discharge from your vagina, tell your doctor immediately.
Take-Home Message
- CVS is a highly accurate test that can detect genetic conditions in the baby early in pregnancy.
- This has advantages (getting results early) as well as minor risks (very small chance of miscarriage and infection).
- This is not a test for everyone. It is usually recommended for those with certain risk factors, such as being over 35 years old.
- Whether or not to have this test is a personal decision between you and your partner. Talk to your doctor carefully and get all the information before making that decision.
- Follow the rest and other instructions given after the test exactly. If you experience any unusual symptoms, inform your doctor immediately.
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