Chorionic villus sampling is one of many early prenatal diagnostic tests that can be done to help parents prepare for delivery and make decisions about the health of their baby and that of the expectant mother. Due to the fact that there are some risks involved with this procedure, it is not a routine test but it done only when circumstances warrant.
What is Chorionic Villus Sampling?
This prenatal test, also known as chorionic villus sampling (CVS), is done during the first trimester of pregnancy to identify any potential problems with the fetus. CVS is typically done at ten to 12 week of pregnancy but can be done as early as eight weeks into the pregnancy if other screening tests or family history warrants earlier detection.
No test can be 100% accurate, however, the result of this test can either reassure a stressed out expectant mom, allow more time to plan for the birth or in some cases, provide the chance to end the pregnancy while it is still relatively safe.
Why Is This Test Performed?
Nearly all chromosomal disorders, in addition to the presence of hundred of genetic disorders, can be detected with 99% accuracy by chorionic villus sampling. This type of test is performed in women over 35 years of age who are considered to be at an increased risk of birthing a baby with chromosomal defects and whenever first trimester screening tests or family history indicate that either parent carries a genetic disorder. Test results identify the presence of genetic disorders like sickle cell disease or hemophilia in addition to chromosomal birth defects like Down syndrome and Klinefelter syndrome.
How Do I Prepare?
Consent forms indicating you were informed of the risks involved and give your consent for the procedure are signed prior to the procedure. An ultrasound will be used to verify that you are far enough along in the pregnancy for proper sampling and to confirm the location of the placenta.
In most cases, you can eat normally prior to your procedure but you may be asked to drink plenty of fluids as a full bladder can sometimes facilitate sampling. It may be a good idea to take someone with you to the appointment for support and to drive you home afterwards. Recovery time may include some cramping and usually involves taking time to rest.
What are the Sampling Collection Methods?
There are two ways to collect the needed tissue sample. The location of the placenta is determined via an ultrasound and is what most often determines which type of sample collection procedure will be used. If the placenta is in a favorable location, transcervical collection is done using a catheter inserted through the cervix.
In the event the ultrasound shows the placenta is not accessible through the cervix or in expectant moms who have other complications, a transvaginal collection will be performed. The placenta is accessed via the abdominal wall with the use of a needle and syringe for transvaginal collection.
What Happens If Results Indicate a Problem?
The tissue sample collected will be analyzed by a lab and results are typically available in fewer than two weeks. In the event test results indicate a problem with the fetus, some tough decisions will need to be made. The decisions you need to make will depend on the type of defect that was detected and your feelings.
Some couples choose to terminate the pregnancy during the first trimester. Other couples view the test results as advanced notice of what will be required and take the remaining months of the pregnancy to learn more about the disorder so they can be better prepared to raise their child.
For many expectant mothers, chorionic villus sampling may not be necessary. In the event that it does become necessary, understanding the facts about what it is and why it’s used may help to reduce anxiety prior to testing.