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Q: What is the difference between the CVS test and amniocentesis? Do I need both tests?
A: The difference is one of timing, and you won’t need to take both tests. In fact, you might not need either one.
These tests are generally recommended if your developing fetus is at higher risk for genetic abnormalities or other health issues, such as if you:
- Are 35 or older
- Tested positive in a noninvasive prenatal screening test (a blood test conducted in the first trimester that also checks for genetic abnormalities)
- Had a previous pregnancy involving Down syndrome or a neural tube defect (a serious condition affecting the baby’s brain or spinal cord)
- Have a family history of a specific genetic condition
- Had an ultrasound that indicated possible abnormalities
Chorionic villus sampling (or CVS) can be done in the first trimester (at 10 weeks or later). The specialist who performs the CVS will insert a needle through your abdominal wall, or a long thin tube (a catheter) into your vagina and through your cervix.
These devices extract samples of chorionic villi, tiny pieces of tissue attached to your placenta that share your baby’s genetic makeup. The tissue samples are tested to check for health issues (including Down syndrome and other chromosomal abnormalities) in the baby.
Amniocentesis is usually performed in the second trimester (during weeks 15–20 of pregnancy). In this test, a thin needle is inserted through your abdominal wall and into the uterus, using ultrasound imaging as a guide.
The needle will draw a small amount of amniotic fluid into a syringe. The fluid is then tested for certain conditions (including Down syndrome and neural tube defects).
Learn more about tests administered during pregnancy to check for potential health problems.
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