Screening test for Down's syndrome
Karen Starkey, M.D., is an OB/GYN physician for Banner Ironwood Medical Center. She can be reached at (480) 394-4620.
Question: Should I have a screening test for Down’s syndrome during my pregnancy?
Answer: Down’s syndrome is a genetic disorder in which the fetus carries an extra number 21 chromosome. It occurs in about 1 in 700 births. Although the risk for having a child with Down’s increases with the mother’s age, a woman of any age can have a child with Down’s syndrome.
The American College of Obstetricians and Gynecologists recommends that all pregnant women, regardless of age, be offered the opportunity to have a screening test for Down’s syndrome before 20 weeks of pregnancy. While these voluntary tests tell you the chances of your fetus having Down’s, they cannot tell you for certain whether your fetus actually has the syndrome. Only diagnostic tests such as CVS and amniocentesis can tell you this for certain. These are invasive tests, however, and carry a small risk of miscarriage (0.5 to 1 percent).
Most people who have a have a screening test for Down’s have a “negative” result, meaning their fetus is at low risk for the syndrome. It does not, however, guarantee that the fetus does not have Down’s.
A positive screening test result merely indicates an increased risk of having a fetus with Down’s. In this case, you may then elect to undergo diagnostic testing (CVS in the first trimester and amniocentesis in the second trimester) if you want to know for certain.