Chorionic villus sampling (CVS) is a procedure in which a small amount of tissue (chorionic villi) is obtained from the developing placenta between weeks 11 and 14 of pregnancy; however, it can be throughout pregnancy if necessary. The tissue is then sent to a lab for chromosomal analysis and, if necessary, specific genetic diseases. One advantage of CVS is that this test can be performed much earlier along in pregnancy than amniocentesis.

A disadvantage is that CVS does not detect neural tube defects, such as spina bifida. However, an alpha-fetoprotein (AFP) test and a high-resolution ultrasound examination can be performed later in your pregnancy to screen for these defects.

In addition, approximately one percent of CVS test results are considered unclear or indeterminate. Most of the fetuses in these pregnancies are normal, but additional testing—including amniocentesis—may be indicated.

CVS is offered for:

• Women who will be 35 years of age or older at the time of delivery
• Couples with a previous child or other family member with a chromosomal abnormality
• Couples in which one partner has a chromosomal rearrangement (for example, a translocation or an inversion)
• Couples at increased risk of having a child with a genetic disease for which testing is available

To learn more about CVS and determine if you would benefit from this test, please speak with your obstetrician or contact our office directly.