Amniocentesis is a procedure where fluid is aspirated out of the amniotic sac. The amniotic sac is the fluid-filled structure inside the pregnant uterus where the fetus grows. Fetal urine, fetal cells, and various proteins move freely within this sac. During amniocentesis, a long needle is placed through the abdominal wall and into the amniotic sac. Once the needle is in the amniotic sac, a syringe is used to aspirate the amniotic fluid. The fluid is then sent for evaluation. New technologies provide amniocentesis needles that automatically protect the user from needlesticks.