What are prenatal screening test for chromosomal disorders?
Screening tests done in the first or second trimester can predict the chances of chromosomal conditions. These tests (such as the “quad” or “triple” screen, or the more recent first trimester test that includes nuchal translucency) provide only an estimate of chance. These tests will not tell you for certain whether you will have a baby with Down syndrome. Instead, you will just receive the probability of having such a child. For example, you screening results might report a ration of 1/200, meaning that you have 1 in a 200 chance of having a baby with Down syndrome. If you results on the screening tests show that your chances of having a baby with Down syndrome are higher than average, your doctor may suggest a diagnostic test. What are diagnostic tests for? Unlike test of the mother’s blood, there are two tests that tell you whether or not you will have a baby with Down syndrome: an amniocentesis and chorionic villus sampling (CVS). During an amniocentesis, your obstetrician removes
