Prenatal Tests and Procedures – Diagnostic Tests
Diagnostic tests can give definite “yes” or “no” answers about whether your baby has a birth defect. But, unlike screening tests, they are invasive or come with a risk of miscarriage. Amniocentesis and chorionic villus sampling (CVS) are the two most commonly used. Both tests are more than 99% accurate for finding these problems. These tests also can tell you your baby’s sex. In most cases, results take about two weeks.
Amniocentesis
This test is performed in pregnancies of at least 16 weeks. It involves your doctor inserting a thin needle through your wife’s abdomen, into her uterus, and into the amniotic sac to take out a small amount of amniotic fluid for testing. The cells from the fluid are grown in a lab to look for problems with chromosomes. The fluid also can be tested for AFP. About 1 in 200 women have a miscarriage as a result of this test.
Chorionic villus sampling (CVS)
This test is performed between 10 and 12 weeks of pregnancy. The doctor inserts a needle through your wife’s abdomen or inserts a catheter through her cervix in order to reach the placenta. The doctor then takes a sample of cells from the placenta. These cells are used in a lab to look for problems with chromosomes. This test cannot find out whether your baby has open neural tube defects. About 1 in 200 women have a miscarriage as a result of this test.