What to Expect From Prenatal Genetic Testing

• you will be 35 years of age or older at delivery
• your family has a known genetic disorder
• you have had a previous child with a birth defect
• you and your partner are carriers of the same recessive disorder
• other indications as directed by your obstetrician

Both CVS and amniocentesis can cause cramping, and a small number of women have miscarriages following the procedures (the risk is slightly higher with CVS).

CVS is performed at 10 to 12 weeks of gestation and involves analyzing a sample of placental tissue. A thin tube inserted through the vagina and cervix, or the abdomen, and is used to suction out a small tissue sample from the placenta. However, unlike amniocentesis, CVS cannot be used to test for neural tube defects, such as spina bifida and anencephaly. Therefore, it's usually recommended that a woman undergoing CVS also have the prenatal blood test called the maternal serum alpha fetoprotein (MSAFP) screening test, at about 16 to18 weeks of pregnancy.

CVS is more attractive to some women because it can be done earlier than amniocentesis. Many women say that this is a time when pregnancy is still a private issue. But other women feel the slightly higher risk of CVS is unacceptable, and they wait for the amniocentesis. Amniocentesis and CVS can be used to prenatally diagnose many, but not all, genetic disorders.
Every prenatal screening and diagnostic test has its benefits, risks and limitations. It is very important to discuss these testing options with your doctor and, if possible, a genetic counselor.