Chorionic villus sampling (CVS) is a test that can detect chromosomal abnormalities such as Down syndrome and a host of other genetic disorders in a developing fetus. The test is offered to women who are at risk of having a baby with these disorders or because they or their partner have a genetic disorder. CVS provides much of the same information as an amniocentesis but can be done about a month earlier, between 10 and 12 weeks of pregnancy.
CVS involves getting a very small sample, or biopsy, of the chorionic villi cells in the placenta and sending it to a lab for genetic analysis. The genetic material in chorionic villi cells – DNA, chromosomes and enzymes - is the same as that in the baby's cells.
CVS can be used to find:
- Chromosomal defects such as Down syndrome, trisomy 13, trisomy 18, and sex chromosome abnormalities like Turner syndrome and Klinefelter syndrome; the test is more than 99% accurate in diagnosing these conditions.
- Genetic disorders such as Tay-Sachs disease, hemophilia, sickle cell disease or cystic fibrosis.
- The sex of your baby if you might have a gender-related genetic disorder such as hemophilia, which a mother only passes to her male children.
- Unlike amniocentesis, CVS cannot detect neural tube defects such as spina bifida. The test can also not check the development of the baby's lungs.
Before having CVS, you will meet with our genetic counselor who will explain the procedure, the risks involved and possible results.
The procedure itself is done either by placing a thin, flexible tube through the vagina and cervix into the placenta or by inserting a needle through the abdominal wall into the placenta. Ultrasound is used to guide the tube or needle into the right spot.
CVS may cause some of the baby's blood cells to enter your bloodstream. If you have Rh-negative blood, you will have blood taken before the CVS procedure and will also receive a shot of Rhogam afterwards to prevent you from producing antibodies against your baby's blood cells.
After a CVS
You may experience:
- Some tenderness where the needle was inserted
- Some minor cramping (less than a menstrual period)
- Some bleeding or spotting that should stop within a few days There is a slight risk of miscarriage, infection and amniotic fluid leakage as a result of the procedure. If you experience a fever, excessive bleeding or vaginal discharge after your CVS, please call your health care provider.
What do normal results mean?
A normal CVS result means there are no signs of any genetic defects in your baby. Please note, however, that the test could miss some genetic defects.
What do abnormal results mean?
If your CVS results are abnormal, it may be a sign of more than 200 disorders, including Down syndrome, hemoglobinopathies, and Tay-Sachs disease.
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Prenatal Diagnosis Center
Bay Tower Medical Center
101 Plain Street
Providence, RI 02905