Chorionic villus sampling is a test that is done during early pregnancy to test for chromosomal abnormalities in the fetus. It involves removing chorionic villi from the placenta. The placenta is the organ that provides nutrients and oxygen to the baby during pregnancy. It also removes waste from the baby’s blood. Chorionic villi is the tissue that makes up most of the placenta. The test is done during the 9th-13th weeks of pregnancy.
Reasons for Test
Chorionic villi contains valuable information about the baby’s genes. By testing chorionic villi, the doctor can find out if the baby has a chromosomal abnormality, like Down syndrome . The test can also detect genetic disorders, like cystic fibrosis . It cannot detect neural tube defects, such as spina bifida .
This test may be considered when:
- Other tests, such as a first trimester ultrasound or blood tests reveal abnormal results
- A prior pregnancy had a chromosomal abnormality
- The mother is 35 years old or older
- You or your partner is a carrier for a genetic disorder
- There is a family history of a genetic disorder
When the results of this testing are available, you will need to consider what you will do with the information. If the test shows that your baby may have a genetic disorder, it may require you to make tough decisions regarding your pregnancy, such as whether or not to continue it. If you do continue with the pregnancy, you will need to address concerns, such as planning for a child with special needs. Your doctor can help you understand the pros and cons of having this test, as well as talk to you about options after you know the results.
There are some risks with this test:
- Bleeding from the vagina
- Sensitivity to your baby’s blood, which may enter your bloodstream, also called Rh incompatibility
- Infection in the uterus
Chorionic villus sampling may not be recommended if you:
- Have an active infection, like a sexually transmitted disease
- Are carrying twins
- Have experienced bleeding from the vagina during pregnancy
What to Expect
Prior to Test
Since you may need to have a full bladder, drink plenty of fluids before the test. However, depending on how your placenta is positioned, you may be asked to urinate before the test. Talk with your doctor about specific ways to prepare for the test. Also, arrange to have someone drive you home from the hospital.
Description of Test
An ultrasound will be used to find the position of your placenta and take measurements to determine the age of the fetus. An ultrasound uses sound waves to create images of structures inside the body.
Your abdomen will be cleansed with antiseptic. Using the ultrasound images as a guide, a long, thin needle will be inserted through your abdominal wall. The needle will enter your uterus, avoiding the baby. You may feel cramping at this time. A tissue sample from your placenta will be withdrawn into a syringe through the needle.
Your baby's heart rate may be monitored using an ultrasound. You will be encouraged to rest when you are home. You will most likely be able to return to normal activities the next day. If you have a RH negative blood type, you will need to receive Rhgam to prevent a condition called isoimmunization.
How Long Will It Take?
Will It Hurt?
You may feel some cramping during and after the test. You may also have a small amount of bleeding right after the test.
It may take 1-2 weeks to receive your test results. You will go over your results with your doctor or a genetic counselor.
If the test results are unclear, you may need to have another test called an amniocentesis . This is to help get a better understanding of the results.
If the results show that your baby has a genetic disorder or problems with chromosomes, you and your doctor will discuss how to manage your pregnancy. This may be a stressful time. Seeking support from your family, friends, and healthcare team can help.
Call Your Doctor
It is important to monitor your recovery. Alert your doctor to any problems. If any of the following occur, call your doctor:
- Heavy bleeding from your vagina
- Leaking of amniotic fluid
- Uterine contractions
If you think you have an emergency, call for emergency medical help right away.
- Reviewer: Marcie L. Sidman, MD
- Review Date: 03/2016 -
- Update Date: 04/30/2014 -