Amniocentesis (amniotic fluid test)
Reviewed
Amniocentesis is a diagnostic test done during pregnancy (usually between weeks 15 and 20) that takes a sample of amniotic fluid from the abdomen to diagnose certain genetic disorders, birth defects, and other conditions in the unborn baby. It is a diagnostic test, meaning results are almost always accurate, unlike screening tests which only estimate risk.
Preparation and collection
If you are early in pregnancy, you may be asked not to urinate before the test to keep your bladder full. In later pregnancy, you need an empty bladder.
Understanding this test
Use the reference interval and units printed by the laboratory that performed the test. A result outside that interval is not a diagnosis by itself, and a result inside it does not rule out every condition. Your symptoms, history, medicines, timing, and related tests can change what the result means.
- A normal result does not rule out all possible health problems.
- An abnormal result means your baby very likely has the disorder, but your provider may order more tests to confirm or learn more about your baby's health.
- There is a very slight risk (less than 1 percent) of causing a miscarriage.
What to do next
Your provider will explain your test results. It may help to speak with a genetic counselor before testing and/or after you get your results.
Evidence source
U.S. National Library of Medicine: Amniocentesis (amniotic fluid test)