If a couple is expecting a baby, a mother can be screened with tests to determine if the baby will inherit the Tay-Sachs gene.   Mothers can have their unborn baby tested for the Hex A insufficiency that causes Tay-Sachs Disease.  If the test does not detect Hex A, the child will be born with Tay-Sachs.  If the test does detect Hex A, the baby will not have Tay-Sachs.  Between ten and twelve weeks of pregnancy, a mother expecting a baby can get a chorionic villus sampling, or CVS, in which a small sample of the placenta is drawn into a needle for testing.  Between fifteen and eighteen weeks of pregnancy, the mother can also have an amniocentesis to screen for the Tay-Sachs gene. In this test, a needle is inserted into the mother's belly to draw a sample of the amniotic fluid that surrounds the fetus.