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Pronounced: am-KNEE-o-sen-TEE-sis
En Español (Spanish Version)

Definition | Reasons for Procedure | Possible Complications | What to Expect | Call Your Doctor


Amniotic fluid surrounds the baby during pregnancy. Amniocentesis is the removal of a small amount of this fluid for testing.


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Reasons for Procedure

Amniocentesis is most often done to see if there is an abnormality in your baby's genes (DNA). It can also be done to see if your baby is developing correctly.

Factors that indicate that you may need this procedure include:

  • Age: over 35 years at the time of delivery
  • Family history of chromosome abnormality
  • Family history of inherited disorder
  • Family history of neural tube defect (problems in spine and brain growth, such as spina bifida or anencephaly)
  • Abnormal results from an earlier blood screening test, such as maternal serum alpha-fetoprotein (AFP)

Depending on your risk factors, cells in the amniotic fluid are tested for:

  • Chromosome abnormalities. The results are usually ready within 14 days. Missing or extra chromosomes lead to physical birth defects and intellectual disability. Down's syndrome is one example.
  • Inherited genetic diseases—Test results are usually ready in 1-5 weeks. Examples include:

Amniocentesis may also be done:

  • To determine whether the baby's lungs are mature
  • In high-risk pregnancies that may require early delivery

Possible Complications

Complications that may occur with an amniocentesis include:

  • Miscarriage —Extremely rare
  • Bleeding, cramping, and leaking fluid from the vagina
  • Infection
  • Mixing of blood if you and your baby have different blood types
  • Need for repeat testing
  • Harm to the fetus by needle—Rare

Factors that may increase your risk of complications include:

  • Maternal obesity
  • Previous abdominal surgery

Be sure to discuss these risks with your doctor before the procedure.

What to Expect

Your doctor may give you local anesthesia. This numbs a small area in the abdomen where the needle will be placed.

This is usually done when you are 16 weeks pregnant. It is done later in the pregnancy when checking your baby's lung maturity.

First, your doctor will do an ultrasound. This will help to choose a safe spot to insert the needle. Your abdomen will be cleaned. Next, the doctor will insert a very thin needle through your abdomen into your uterus. A few teaspoons of amniotic fluid will be taken out. After the needle is removed, the doctor will make sure that your baby's heartbeat is normal. In most cases, an ultrasound will be used throughout the procedure.

About 45 minutes.

You may feel cramping when the needle enters your abdomen. You may also feel pressure when the fluid is withdrawn.

When you return home after the procedure, do the following to help ensure a smooth recovery:

  • For the first few hours, avoid physical stress.
  • Rest for the first 24 hours, avoiding heavy exercise and sexual activity.
  • Follow your doctor's instructions .

A test showing a healthy baby is ideal. But, you will need to be prepared if the results show otherwise. If the test shows that your baby may have a genetic disorder, you may need to make tough decisions regarding your pregnancy. If you do continue with the pregnancy, then you will need to address your child's special needs. Your doctor can help you understand the pros and cons of having this test. He or she will work with you on options that are best for you once you know the results.

Call Your Doctor

After arriving home, contact your doctor if you have:

  • Signs of infection, including fever and chills
  • Nausea or vomiting
  • Pain or cramping in your lower abdomen or shoulder
  • Vaginal bleeding or a loss of fluid from the vagina
  • Redness, swelling, increasing pain, excessive bleeding, or discharge from the amniocentesis site
  • New, unexplained symptoms

In case of an emergency, call for medical help right away.


American Congress of Obstetricians and Gynecologists


American Pregnancy Association



Canadian Women's Health Network


The Society of Obstetricians and Gynaecologists of Canada



The American College of Obstetricians and Gynecologists, Invasive Prenatal Testing for Aneuploidy, Practice Bulletin No. 88, December 2007; Reaffirmed 2009.

Chorionic villus sampling (CVS). American Pregnancy Association website. Available at: http://www.americanpregnancy.org/prenataltesting/cvs.html. Updated April 2006. Accessed October 2, 2012.

Later childbearing. American College of Obstetricians and Gynecologists website. Available at: http://www.acog.org/~/media/For%20Patients/faq060.pdf?dmc=1&ts=20121002T1240392696. Accessed October 2, 2012.

Screening and monitoring during pregnancy. EBSCO DynaMed website. Available at: http://dynamed.ebscohost.com/. Updated September 14, 2012. Accessed October 2, 2012.

Last reviewed October 2012 by Andrea Chisholm

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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