Now that you’re pregnant, you have a lot to plan for. Part of that is the prenatal care you’ll need.
Depending on your age, health, and other factors, your doctor may recommend routine and individualized prenatal tests to help monitor the health of your growing baby.
Two main categories of tests you may have during pregnancy include screening and diagnostic. Screening tests are more general and help your doctor determine your baby’s health in the womb.
If your doctor suspects that the developing fetus may have a health condition, they may recommend specific diagnostic tests to confirm screening test results.
Chorionic villus sampling (CVS) is an example of a diagnostic test that checks for specific genetic conditions in a fetus.
Chorionic villus sampling (CVS) is a prenatal diagnostic test that checks for a genetic or chromosomal condition during the first trimester of pregnancy.
With this test, doctors look at cells from the lining of the placenta to determine the health of the baby.
CVS will test for conditions such as:
- cystic fibrosis
- Down syndrome (trisomy 21)
- Duchenne muscular dystrophy
- Edwards syndrome (trisomy 18)
- Patau syndrome (trisomy 13)
- phenylketonuria (PKU)
- sickle cell anemia
- Tay-Sachs disease
A CVS test is completely optional. You may choose to decline it. Parents may decide not to pursue optional testing for many reasons, from religious beliefs to being more comfortable with unexpected outcomes in their pregnancy.
CVS is not a test offered to everyone during pregnancy. It may be performed if, based on other screening test results, the baby is thought to be at risk of a genetic condition.
If you’re pregnant, your doctor may recommend CVS if you have a family history of certain genetic conditions, or if a screening test in the first trimester showed results that may indicate a genetic condition.
Before recommending a CVS test, a doctor will typically look for certain risk factors, such as:
- abnormal blood screening test results
- abnormal follow-up ultrasound scan
- family history of a genetic condition
- medical history of your other children
- high risk pregnancy for other reasons
- older maternal age at the time of pregnancy (35 years or older)
One main benefit to CVS is that it may be performed earlier in your pregnancy, between weeks 10 and 13.
The results of CVS may be used to help make decisions about whether to continue a pregnancy while still in the first trimester. If a fetus has a genetic or chromosomal issue, it may lead to other health conditions or complications.
Another benefit of determining whether a baby has a certain genetic condition is the ability to plan for any healthcare needs these conditions may cause during and after birth.
You may also want to learn more about any condition your baby has and begin to find resources, such as support groups and other healthcare professionals, your baby may need.
During a CVS test, a few cells from the inner lining of the placenta, called the chorionic villus, are removed and carefully examined and tested.
During amniocentesis, another kind of diagnostic test, a small sample of the amniotic fluid — the fluid that surrounds the growing fetus — is removed and then tested.
Amniocentesis tests fetal cells contained within the amniotic fluid and the levels of certain proteins to check for certain genetic changes.
If you opt to have a CVS test, it can be done earlier in your pregnancy than amniocentesis, which is typically performed a few weeks later at around 15 weeks.
Unlike a CVS test, amniocentesis can be used to test for other conditions, including spina bifida, a brain and spinal cord condition.
There’s nothing you need to do to prepare for CVS. You can eat and drink as you usually do. You will not be sedated during the test, so you can drive yourself to and from the doctor’s office.
Ask your doctor about what to expect during the test and afterward. Also, discuss other diagnostic options for the CVS test.
Your doctor will likely refer you to a genetic counselor who can provide in-depth information about genetic conditions that may be present in some families or happen on their own.
The CVS test is carried out early in pregnancy, typically between weeks 10 and 13. During this minor procedure, your doctor will safely remove a tiny placenta cell sample by one of two methods:
- Transabdominal CVS: a placenta sample is taken by inserting a needle through the abdomen into the uterus and placenta
- Transcervical CVS: a placenta sample is taken by inserting a thin tube through the cervix and into the placenta
The method used to obtain the sample will depend on a few things, such as where the placenta is located and your body weight.
The most common method is the transabdominal CVS. Both methods are very quick, and this procedure is normally not painful. You may feel mild discomfort and have some cramping after the test.
It will only take a week or two to get the results of the CVS test. If there’s a rarer condition present, testing may take longer. In most cases, the results of a CVS test are considered to be almost 99% accurate.
Follow up with your doctor right away if you experience any unusual side effects, such as:
- fluid leakage
There are a few rare but serious side effects caused by CVS.
Your doctor will walk you through the side effects that may occur. You and your partner can ask them any questions to decide whether you would like to go ahead with the procedure.
The main risks from this procedure are:
- Rhesus sensitization
- repeat procedure and test if sample is too small
In some cases, retesting may be needed if the results are uncertain.
The results of your CVS test results may indicate if your baby will be born with certain conditions.
It’s important to note CVS can only be used to detect specific conditions. You may need further blood tests in the future to test for other conditions, including neural tube changes.
Pregnancy can be an exciting and uncertain journey for any parent. Prenatal testing is designed to help you have a healthy and informed pregnancy. Tests such as the CVS can help diagnose some genetic changes before your baby is born.
It’s important to have an open dialogue with your doctor about any concerns you have. Remember that the CVS test is an option for you. You can choose to decline the test if you are concerned about the procedure.