You may want to talk to a genetic counselor before or after the test. This person is trained to give you detailed information about the test. The counselor can help you make decisions about testing. The counselor can also help you understand the results of the tests.

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

Amniocentesis, Opens dialog is done by your obstetrician in the doctor's office or in the hospital. You probably won't need to stay overnight in the hospital unless problems occur during the test.

You will lie on your back on an exam table. Your belly will be cleaned with an antiseptic.

Your doctor will use a fetal ultrasound, Opens dialog to check the position of your fetus and the placenta, Opens dialog. 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.

With the ultrasound picture as a guide, your doctor will gently put a thin needle through your belly and into your uterus. This will not hurt your fetus or the placenta. If your fetus moves too close to the needle, the doctor will take the needle out and try again in another spot.

The doctor will take about 2 Tbsp (30 mL) of amniotic fluid. Then the needle is removed. The site is covered with a bandage.

Your fetus's heart rate and your blood pressure, pulse, and breathing will be checked before, during, and after the test.

How long the test takes

The test will take about 15 minutes. The thin needle is in your belly for only 1 to 2 minutes.

You may feel a sharp sting or burn in your belly where the needle is put in. This lasts for only a few seconds. When the needle is put into your uterus, you may feel a sharp cramp for a few seconds.

When the amniotic fluid is taken out, you may get a feeling of pulling or pressure in your belly. To keep yourself comfortable, breathe slowly and relax your belly muscles during the test.

Some risks of amniocentesis may include:

• Leakage of amniotic fluid.
• Vaginal bleeding.
• Infection in the uterus.
• Miscarriage. About 3 out of 1000 women have a miscarriage after this test.^{footnote 1}

Amniocentesis has a very small risk of causing bleeding that could mix your blood and your fetus's blood. So if you have Rh-negative blood, you will be given the Rh immunoglobulin shot (such as RhoGAM). This can prevent Rh sensitization, which could cause harm if your baby has Rh-positive blood.

Normal amniotic fluid is clear to light yellow in color and does not contain any harmful bacteria. The cells can be tested for problems.

• Cells from your fetus are looked at carefully. They are checked for the proper number and arrangement of the cell parts (chromosomes, Opens dialog) that show genetic disease. Normally there are 46 chromosomes in each cell, arranged in 23 pairs. Chromosomes also tell the sex of your fetus.
• The amounts of some substances in the amniotic fluid may be measured. These results can find some birth defects, genetic diseases, and the maturity of your fetus.

Normal results from amniocentesis do not guarantee that your baby will be healthy.