Amniocentesis is a procedure in which your doctor removes a small amount of amniotic fluid from your uterus. The amount of fluid removed is typically no more than 1 ounce. Amniotic fluid surrounds your baby in the womb. This fluid contains some of your baby’s cells and is used to find out if your baby has any genetic abnormalities. This type of amniocentesis is usually performed in the second trimester, typically after week 15. It can also be used to determine if your baby’s lungs are mature enough to survive outside the womb. This type of amniocentesis would occur later in your pregnancy. Your doctor will use a long, thin needle to collect a small amount of amniotic fluid. This fluid surrounds and protects the baby while they’re in your womb. A laboratory technician will then test the fluid for certain genetic disorders, including Down syndrome, spina bifida, and cystic fibrosis. The test results can help you make decisions about your pregnancy. In the third trimester, the test can also tell you whether or not your baby is mature enough to be born