Amniocentesis is a procedure in which amniotic fluid is removed from the uterus for testing or treatment. Amniotic fluid is the fluid that surrounds and protects a baby during pregnancy. This fluid contains fetal cells and various chemicals produced by the baby.Amniocentesis can be done for various reasons:With genetic amniocentesis, a sample of amniotic fluid is tested for certain conditions - such as Down syndrome and spina bifida.With maturity amniocentesis, a sample of amniotic fluid is tested to determine whether the baby's lungs are mature enough for birth.Occasionally, amniocentesis is used to evaluate a baby for infection or other illness.Rarely, amniocentesis is used to decrease the volume of amniotic fluid.Although amniocentesis can provide valuable information about your baby's health, the decision to pursue invasive diagnostic testing is serious. It's important to understand the risks of amniocentesis - and be prepared for the results.