What is Down Syndrome?

Chorionic Villus Sampling (CVS)

This test involves obtaining cells from the developing placenta instead of from the amniotic fluid. It is done early in pregnancy, between 10 and 12 weeks. An ultrasound picture locates the placenta in the uterus. A tiny piece of tissue is then removed from the placenta. This is done using a thin needle through the abdomen or a slender tube through the cervix. The cells from the placenta are examined for chromosomal defects.

There is a risk of miscarriage: about 1 to 3 per 100. The final results are available in two weeks. CVS is 98% accurate for the diagnosis of Down syndrome and other chromosomal defects. CVS cannot detect neural tube defects. An AFP blood test is recommended at 15-20 weeks of pregnancy to screen for these defects.

There is a risk of miscarriage: about 1 to 3 per 100. The final results are available in two weeks. CVS is 98% accurate for the diagnosis of Down syndrome and other chromosomal defects. CVS cannot detect neural tube defects. An AFP blood test is recom

Reference Sources:
"Prenatal Diagnosis of Birth Defects: Amniocentesis" (Videotape)
"Prenatal Testing Choices For Women 35 Years and Older" (Brochure)
California Department of Health Services
Genetic Disease Branch