Is There an Alternative?
Amniocentesis is another option for prenatal testing and is usually done between 15 to 18 weeks of pregnancy. Amniocentesis can be used to test for the same genetic disorders and chromosomal abnormalities as the CVS. It can also check for open neural tube defects, which the CVS does not. However, patients having a CVS undergo a blood test for alpha fetoprotein (between 15 to 17 weeks gestation) and a detailed ultrasound, which can identify 90 to 95 percent of open neural tube defects. The risk of miscarriage following an amniocentesis may be slightly less than CVS.