Chorionic villus sampling is a test that is done during early pregnancy to test for chromosomal problems 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.
Nine Week Old Fetus in Utero
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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
revealed 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
Although a test showing a healthy baby without a genetic disorder is ideal, you will need to be prepared if the results show otherwise. 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 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 about your options after you know the results.
There are some risks with having this test, such as:
- Bleeding from the vagina
Sensitivity to your baby’s blood, which may enter your bloodstream, also called
- Infection in the uterus
Chorionic villus sampling through the cervix may not be recommended if you:
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.
The doctor will use an ultrasound 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.
The doctor will use the ultrasound images as a guide to take a tissue sample from your placenta. First, your vagina and cervix will be cleansed with antiseptic. Next, a device called a speculum will be inserted to widen the opening of the vagina. A thin, hollow tube will be inserted through your vagina and cervix. When it reaches the placenta, it will gently suction a small tissue sample. You may feel cramping while the sample is being taken.
The doctor may want to monitor your baby’s heart rate 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 Rhogam to prevent a condition called isoimmunization.
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 the results with your doctor or a genetic counselor.
If the test results are unclear, you may need to have another test, called an
to give you a better understanding of the results.
If the results show that your baby has a genetic disorder or chromosomal problems, you and your doctor will discuss how to manage your pregnancy. This may be a stressful time. Get support from your family, friends, and healthcare team.
After the test, call your doctor if any of the following occurs:
- Heavy bleeding from your vagina
- Leaking of amniotic fluid
- Uterine contractions
If you think you have an emergency, call for medical help right away.
Last reviewed March 2013 by Andrea Chisholm, MD
Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.
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