Amniocentesis (amniotic fluid test)
Reviewed
Also called: amniotic fluid analysis, amniotic fluid test
Amniocentesis is a test done during pregnancy. It is used to diagnose certain genetic disorders, birth defects, and other conditions in your unborn baby.
Specimen: amniotic fluid
Urgent safety information
Your provider will let you know if there are any symptoms that you should tell them about. These may include ongoing vaginal bleeding, amniotic fluid leakage, severe cramping, or a fever.
Why this test may be ordered
- You are age 35 or older (risk of genetic disorders increases with age)
- A prenatal screening test 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
Preparation and collection
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. In later pregnancy, you need to have an empty bladder for the test.
Ultrasound uses sound waves to show the position of your baby and placenta so your provider can see where to take a sample of amniotic fluid. Your provider will insert a thin needle into your belly, withdraw a small amount of amniotic fluid, and then remove the needle. The procedure usually takes about 15 minutes. Afterward, you may be told not to exercise or have sex for a day or two.
You may feel mild stinging, pressure, and/or cramping during the test. Afterward, you may have mild discomfort or vaginal bleeding, or a small amount of amniotic fluid may leak from your vagina. The risk of serious complications is extremely low. Amniocentesis does have a very slight risk (less than 1 percent) of causing a miscarriage.
Understanding results
Amniotic fluid may be tested for many different disorders. Your test results will depend on which tests your provider ordered.
- Negative (normal): Normal results are reported as "normal" or "negative." This means that it's very unlikely that your baby has the disorder that was tested, but it does not guarantee your baby will not have any health problems. Limitation: Amniocentesis is very accurate, but in certain cases, your provider may order more tests to learn about your baby's health. Next step: Your provider will explain your test results.
- Positive (abnormal): Results that are not normal are reported as "abnormal" or "positive." This means that your baby very likely has the disorder that was tested. Limitation: Amniocentesis is very accurate, but in certain cases, your provider may order more tests to learn about your baby's health. Next step: It may help to speak to a genetic counselor before testing and/or after you get your results.
- 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 to a genetic counselor before testing and/or after you get your results.
- What specific disorders was my amniotic fluid tested for?
- What do my results mean for my baby's health?
- Do I need any follow-up tests?
- Should I speak with a genetic counselor?
Evidence source
Source: U.S. National Library of Medicine (MedlinePlus). Practices and reference ranges may differ in your country.
U.S. National Library of Medicine: Amniocentesis (amniotic fluid test)