Definition: Amniocentesis is a test during pregnancy that removes a small amount of fluid from the sac around the baby to look for birth defects and chromosome problems.
Alternative Names: Culture - amniotic fluid; Culture - amniotic cells
How the test is performed: The health care provider will find the exact location of the baby, usually by ultrasound (see pregnancy ultrasound ). The skin of the abdomen is scrubbed. A numbing medication (anesthetic) may be applied to the skin, or a local anesthetic may be injected into the skin. A long, thin needle is inserted through the abdomen and into the uterus. A small amount of fluid is taken from the fluid-filled sac that surrounds the fetus.
How to prepare for the test: This test is done on the same day -- you will not need to stay overnight in the hospital. You must sign a consent form. Your bladder must be full for the ultrasound. There are no food or drink restrictions. You may need to provide a blood sample to determine your blood type and Rh factor. You may get an injection of a medication called Rhogam if you are Rh negative.
How the test will feel: If an anesthetic is used, you may feel a sharp, stinging sensation for a few seconds. When the needle enters the amniotic sac, you may feel a sharp pain lasting a few seconds. Some women feel pressure in the lower abdomen when the fluid is pulled out. After the procedure, you may have some minor cramping.
Why the test is performed: The test can find chromosome problems such as: Later on in a pregnancy, the test may be used to find problems such as: Late in the pregnancy, this test can determine whether the baby's lungs are developed.
Normal Values: Note: Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.
What abnormal results mean: Amniocentesis can be used to diagnose a large number of gene and chromosome problems in the baby. In addition, it can help diagnose the severity of: - Lung maturity
- Neural tube defects (such as spina bifida)
- Rh incompatibility
DNA testing is available for many diseases. New diseases are being added to this list as genetic research advances. Ask your obstetrician or geneticist if you have a question about a specific disease.
What the risks are: Risks are minimal, but may include: This test is typically done when a problem is suspected, so the benefits outweigh the risks.
Special considerations: There may be alternatives to the amniocentesis. Discuss these other tests with your health care provider.
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