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Amniocentesis
Amniocentesis


Amniocentesis
Amniocentesis


Amniocentesis - series
Amniocentesis - series


Amniocentesis

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:

Amniocentesis is done on an outpatient basis. You do not need to stay in the hospital.

The doctor will find the exact location of the baby, usually by performing a pregnancy ultrasound .

The health care provider will clean an area of skin on the mother's belly area. A numbing medication (anesthetic) may be applied to the skin, or a local anesthetic may be injected into the skin.

The doctor inserts a long, thin needle through the abdomen and into the womb (uterus). A small amount of fluid is taken from the fluid-filled sac that surrounds the baby.



How to prepare for the test:

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.

You will need to sign a consent form before the test.



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:

This test is also sometimes done later in pregnancy to determine whether the baby's lungs are developed if there is a condition that requires early delivery.



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:

  • Determine how well the baby's lungs are developed
  • Diagnose neural tube defects (such as spina bifida)
  • Diagnose Rh incompatibility

DNA testing is available for many of the diseases that may be detected during amniocentesis. Ask your obstetrician or geneticist if you have a question about a specific disease.



What the risks are:

Risks are minimal, but may include:

  • Infection or injury to the baby
  • Miscarriage
  • Leaking of amniotic fluid
  • Vaginal bleeding


Special considerations:

There may be alternatives to the amniocentesis. Discuss these other tests with your health care provider.



References:

Simpson JL, OtaƱo L. Prenatal genetic diagnosis. In: Gabbe SG, Niebyl JR, Simpson JL, eds. Obstetrics:Normal and Problem Pregnancies. 5th ed. Philadelphia, Pa: Elsevier Churchill Livingstone; 2007:chap 7.

Druzin ML, Smith JF Jr, Gabbe SG, Reed KL. Antepartum fetal evaluation. In: Gabbe SG, Niebyl JR, Simpson JL, eds. Obstetrics: Normal and Problem Pregnancies. 5th ed. Philadelphia, Pa: Elsevier Churchill Livingstone; 2007:chap 11.

Cunnigham FG, Leveno KL, Bloom SL, et al . Prenatal diagnosis and fetal therapy. In: Cunnigham FG, Leveno KL, Bloom SL, et al, eds. Williams Obstetrics. 22nd ed. New York, NY; McGraw-Hill; 2005:chap 13.




Review Date: 9/2/2009
Reviewed By: Linda J. Vorvick, MD, Medical Director, MEDEX Northwest Division of Physician Assistant Studies, University of Washington, School of Medicine; Susan Storck, MD, FACOG, Chief, Eastside Department of Obstetrics and Gynecology, Group Health Cooperative of Puget Sound, Redmond, Washington; Clinical Teaching Faculty, Department of Obstetrics and Gynecology, University of Washington School of Medicine. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M., Inc.

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