How should I prepare for an amniocentesis?

Follow any instructions your healthcare provider gives you. Make sure your healthcare provider has an accurate and full list of medications you take and any allergies you have.

Your healthcare provider may ask whether your blood type is Rh negative or positive. If needed, your provider will take steps to safeguard against potential issues that can happen when you have a different blood type than your baby.

Your healthcare provider may instruct you to drink a lot of water or go to the bathroom right before your test. Depending on when you have your test, a full or empty bladder can make it easier for providers to safely perform this test.

How is an amniocentesis procedure performed?

For an amniocentesis, you lie on your back with your stomach showing. During this procedure, your healthcare provider:

  1. Cleans a small area on your belly with an antiseptic (to kill germs).
  2. Applies a special gel on your belly.
  3. Moves a wand-like device over the gel to capture ultrasound images of your baby on a nearby monitor.
  4. Inserts a thin, hollow needle through your abdomen and uterus (into the amniotic sac but away from the fetus).
  5. Removes a small amount of fluid through the needle.
  6. Removes the needle from your abdomen.
  7. Monitors your baby’s heartbeat and movement on the ultrasound to ensure they weren’t affected by the procedure.

After the procedure, your healthcare provider sends the amniotic fluid sample for analysis in a laboratory.

How long does an amniocentesis take?

An amniocentesis procedure may take around 20 minutes from start to finish. But the actual sampling process (when the needle is inside your uterus) takes only a minute or two.

Is an amniocentesis painful?

You may be uncomfortable (or feel a sting) when your healthcare provider inserts the needle through your skin. You may also have minor menstrual-like cramping during the procedure. Cramps can last for a few hours after the procedure.

How accurate is an amniocentesis?

The accuracy of amniocentesis approaches 100%. In some cases, certain factors (such as not collecting enough fluid during the test) may mean the lab can’t analyze the amniotic fluid as expected. This is not common.

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