Amniocentesis is a test that can be done during pregnancy to look for these problems in the developing baby:
Culture - amniotic fluid; Culture - amniotic cells; Alpha-fetoprotein - amniocentesis
How the Test is Performed
Amniocentesis removes a small amount of fluid from the sac around the baby in the womb (uterus). It is most often done in a doctor's office or medical center. You do not need to stay in the hospital.
You will have a pregnancy ultrasound first. This helps your health care provider see where the baby is in your womb.
Numbing medicine is then rubbed onto part of your belly. Sometimes, the medicine is given through a shot in the skin on the belly area. The skin is cleaned with a disinfecting liquid.
Your provider inserts a long, thin needle through your belly and into your womb. A small amount of fluid (about 4 teaspoons or 20 milliliters) is removed from the sac surrounding the baby. In most cases, the baby is watched by ultrasound during the procedure.
The fluid is sent to a laboratory. Testing may include:
Results of genetic testing usually take about 2 weeks. Other test results come back in 1 to 3 days.
Sometimes amniocentesis is also used later in pregnancy to:
How to Prepare for the Test
Your bladder may need to be full for the ultrasound. Check with your provider about this.
Before the test, blood may be taken to find out your blood type and Rh factor. You may get a shot of medicine called Rho(D) Immune Globulin (RhoGAM and other brands) if you are Rh negative.
Why the Test is Performed
Amniocentesis is usually offered to women who are at increased risk of having a child with birth defects. This includes women who:
Genetic counseling is recommended before the procedure. This will allow you to:
Amniocentesis can be used to diagnose many different gene and chromosome problems in the baby, including:
A normal result means:
Note: Amniocentesis typically is the most accurate test for genetic conditions and malformation, Although rare, a baby may still have genetic or other types of birth defects, even if amniocentesis results are normal.
What Abnormal Results Mean
An abnormal result may mean your baby has:
Talk to your provider about the meaning of your specific test results. Ask your provider:
Risks are minimal, but may include:
Driscoll DA, Simpson JL, Holzgreve W, Otano L. Genetic screening and prenatal genetic diagnosis. In: Gabbe SG, Niebyl JR, Simpson JL, et al, eds. Obstetrics: Normal and Problem Pregnancies. 7th ed. Philadelphia, PA: Elsevier; 2017:chap 10.
Wapner RJ. Prental diagnosis of congenital disorders. In: Creasy RK, Resnik R, Iams JD, Lockwood CJ, Moore TR, Greene MF, eds. Creasy and Resnik's Maternal-Fetal Medicine: Principles and Practice. 7th ed. Philadelphia, PA: Elsevier Saunders; 2014:chap 30.
Review Date: 7/17/2017
Reviewed By: Cynthia D. White, MD, Fellow American College of Obstetricians and Gynecologists, Group Health Cooperative, Bellevue, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.
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