Amniocentesis is a procedure in which your health care provider uses a needle to remove a small amount of fluid from the amniotic sac. The amniotic sac is a thin sac filled with fluid that surrounds the baby in the uterus when you are pregnant. The sample of fluid is analyzed in the lab.
Amniotic fluid contains cells from the baby.
Early in pregnancy the cells can be tested for certain genetic problems the baby might have. Amniocentesis is sometimes done near the end of a pregnancy to test the maturity of a baby's lungs. When the test is done for genetic screening, it is usually done between the 15th and 18th weeks of pregnancy. Prenatal tests show an increased likelihood of a problem with the baby. You have given birth to a child with Down syndrome or another genetic disorder.