An amniocentesis test can detect chromosomal, genetic disorders or congenital disabilities (sometimes called birth defects) such as: Down syndrome. Tay-Sachs disease. Neural tube defects such as spina bifida or anencephaly. This test can also evaluate: Fetal lung development: This is helpful if you need to give birth sooner than expected to protect the health of you or the fetus. Rh disease: This is a potentially serious condition where you and the fetus have different blood Rh types. Amniocentesis is sometimes used to treat polyhydramnios (when you have too much amniotic fluid). Providers use amniocentesis to remove excess fluid.