Amniocentesis (amniotic fluid test)

Amniocentesis is a test done during pregnancy. A sample of amniotic fluid is taken from your abdomen (belly). It is used to diagnose certain genetic disorders, birth defects, and other conditions in your unborn baby.

The test is usually done between weeks 15 and 20 of pregnancy. Your baby grows in an amniotic sac inside your uterus. The sac is filled with amniotic fluid, a clear or pale yellow liquid.

The fluid that surrounds and protects your baby throughout pregnancy. It also helps with your baby's development and helps keep your baby at the right temperature. The fluid contains cells that can provide important information about your baby's health.

Amniocentesis is a diagnostic test. That means it will tell you whether your baby has a specific health problem, and the results are almost always accurate. Diagnostic tests are different from prenatal screening tests for genetic disorders.

Prenatal screening tests have no risks for you or your baby, but they don't diagnose problems. They can only show if your baby might have a health problem. If a screening test shows your baby could have a problem, your health care provider may recommend amniocentesis or another diagnostic test to find out for sure.

Why this test is done

Having amniocentesis is your choice. You may want this test if you have a higher risk of having a baby with a health problem. You may have a higher risk if:

• You are age 35 or older; the risk of having a baby with a genetic disorder increases with age
• You had a prenatal screening test that showed your baby might have a problem
• You or your partner have a family history of a genetic disorder or neural tube defect
• You or your partner had genetic testing that showed you carry a genetic disorder
• You or your partner have a child with a genetic disorder or birth defect

Amniocentesis isn't right for everyone. Before you decide to get tested, think about how you might feel and what you might do after learning the results.

How to prepare

If you are early in your pregnancy, you may be asked not to urinate (pee) before the test to make sure that you have a full bladder. This helps move the uterus into a better position for the test. In later pregnancy, you need to have an empty bladder for the test.

Other names for this test

amniotic fluid analysis