Amniocentesis (amniotic fluid test)
Reviewed
Also called: amniotic fluid analysis, amniotic fluid test
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.
Specimen: amniotic fluid
Urgent safety information
Contact your provider if you experience ongoing vaginal bleeding, amniotic fluid leakage, severe cramping, or a fever after the procedure.
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 pregnancy, you may be asked not to urinate before the test to keep your bladder full. In later pregnancy, you need an empty bladder.
You lie on your back. An ultrasound is used to show the position of the baby and placenta. A thin needle is inserted into the abdomen to withdraw a small amount of amniotic fluid. The procedure takes about 15 minutes.
You may feel mild stinging, pressure, and/or cramping during the test. Afterward, you may have mild discomfort, vaginal bleeding, or a small amount of amniotic fluid leakage. There is a very slight risk (less than 1 percent) of causing a miscarriage. Serious complications are extremely low. The test results may cause emotional distress, and although very accurate, there is a small chance of false-positive or false-negative results.
Understanding results
Your test results will depend on which disorders your provider tested for. Amniocentesis is very accurate, but in certain cases your provider may order more tests to learn about your baby's health. A genetic counselor can help you understand what your results mean.
- Negative: It is very unlikely that your baby has the disorder that was tested. This does not guarantee your baby will not have any health problems. Limitation: A normal result does not rule out all possible health problems. Next step: Your provider will explain the results and may recommend follow-up as needed.
- Positive: Your baby very likely has the disorder that was tested. Limitation: In certain cases, your provider may order more tests to confirm or learn more about your baby's health. Next step: Your provider will explain the results and discuss next steps. Speaking with a genetic counselor is recommended.
- 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.
- 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
U.S. National Library of Medicine: Amniocentesis (amniotic fluid test)