Amniotic Fluid Analysis- Why am I having this test?
Amniotic fluid analysis is done during pregnancy. The test is used to gather information about the unborn baby (fetus). This allows your health care provider to:
- Assess the maturity of the fetus.
- Investigate the health of the fetus.
- Check the lung development of the fetus to determine the risk for breathing problems at birth (respiratory distress syndrome or RDS).
Amniotic fluid test can also be used to determine your baby’s sex, risk of hereditary diseases, or risk of infection.
Your health care provider may order this test if your pregnancy is considered to be high risk. This test may also be done if you have had an abnormal ultrasound.
What is being tested?
This test examines the fluid that surrounds your baby in the uterus (amniotic fluid).
What kind of sample is taken?
A sample of amniotic fluid from your uterus is removed using a needle (amniocentesis).
How do I prepare for this test?
If you are less than 20 weeks pregnant, you will be asked to have a full bladder for this test. If you are more than 20 weeks pregnant, you will be asked to empty your bladder prior to having the sample collected.
Your health care provider may give you additional instructions to follow before your amniotic fluid is collected.
How is the sample evaluated?
This test checks for a variety of things. The sample is usually evaluated for:
- Fetal
lung maturity. This is done by analyzing the amniotic fluid to determine
whether a substance that keeps the baby’s lungs open (surfactant)
is present, and if so, whether that substance is mature enough to support
the baby’s breathing. The following components and characteristics of
surfactant will be analyzed:
- Lecithin–sphingomyelin (L/S) ratio.
- Phosphatidylglycerol (PG).
- Lamellar body count.
- Microviscosity.
- Genetic and anatomic abnormalities.
- Disorders that are passed along from parent to child (inherited).
- Fetal health status.
- The presence of bacteria.
How are the results reported?
Some of your test results will be reported as positive or negative. Normal results are:
- Negative for bacteria.
- Positive for PG.
Your test results will also be reported in terms of the appearance of the sample. The appearance of the amniotic fluid should be clear, and pale to straw yellow in color.
Other test results will be reported as values. Your health care provider will compare your results to normal ranges that were established after testing a large group of people (reference values). Reference values may vary among labs and hospitals. For this test, common reference values are:
- L/S ratio: 2 or greater.
- Lamellar body count: greater than 30,000.
- Fetal
lung maturity (FLM):
- Mature: less than 260 mPOL.
- Immature: greater than 290 mPOL.
What do the results mean?
The results can help your doctor estimate risk for RDS or determine if there is an amniotic fluid leak.
- Your
baby is unlikely to develop RDS if:
- The L/S ratio is greater than 2 (or 3 if you have diabetes).
- The presence of PG is recorded (only mature lungs produce PG).
- The lamellar body count is greater than 30,000.
- Your
baby is likely to develop RDS if:
- The lamellar body count is less than 10,000.
Bacteria in the amniotic fluid may indicate an infection.
Talk with your health care provider about what your results mean.
Questions to ask your health care provider
Ask your health care provider, or the department that is doing the test:
- When will my results be ready?
- How will I get my results?
- What are my treatment options?
- What other tests do I need?
- What are my next steps?
Summary
- Amniotic fluid analysis is done during pregnancy.
- The test is used to gather information about the unborn baby (fetus).
- Results are commonly used to determine the maturity of your baby’s lungs as well as the risk of infection.
- Talk with your health care provider about what your results mean.
