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Amniocentesis

Why It Is Done

Amniocentesis may be done during your second trimester of pregnancy to find certain birth defects.

You may choose to have this test because:

  • Of your age. As you get older, you have a greater chance of having a baby with a birth defect. Many doctors use 35 and older as the age for higher risk.
  • You want to know for sure if your baby has a certain health problem. This may help you decide early whether you want to continue your pregnancy or make plans to care for a sick child.
  • You or the baby's father carries an abnormal gene that is known to cause a disease, such as Tay-Sachs disease, sickle cell anemia, or cystic fibrosis.
  • You or the baby's father has a family history of a genetic disorder or birth defect.
  • Screening tests suggest that your chance of having a baby with a genetic disorder or birth defect is higher than average.

Amniocentesis can tell the gender of your fetus. This is important when you or the father may be able to pass on a disease that occurs mainly in one gender (sex-linked), such as hemophilia or Duchenne muscular dystrophy, both of which occur mainly in males.

Amniocentesis may be done during your third trimester to:

  • See if your fetus's lungs are mature. This may be done when you may need to deliver early because of a problem with the pregnancy.
  • See whether the amniotic fluid is infected (chorioamnionitis).

How To Prepare

You will be asked to empty your bladder just before the test.

You will need to sign a consent form that says you understand the risks of the test and agree to have it done.

Talk to your doctor about any concerns you have about the need for the test, its risks, how it will be done, or what the results will mean. To help you understand the importance of this test, fill out the medical test information form(What is a PDF document?).

How It Is Done

Amniocentesis camera.gif is done by your obstetrician in his or her office or in the hospital. An overnight stay in the hospital usually is not needed unless problems occur during the test.

You will be asked to expose your belly. You will then lie on your back with it slightly raised to relax your belly muscles. Your lower belly will be cleaned with a special soap.

Your doctor checks the position of your fetus and the placenta with a fetal ultrasound. Ultrasound uses sound waves to make a picture of the uterus, your fetus, and the placenta on a TV screen. Your fetus's heart rate can also be watched during the test using ultrasound. For more information, see the topic Fetal Ultrasound.

WebMD Medical Reference from Healthwise

Last Updated: April 04, 2012
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

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