What is amniocentesis?
Amniocentesis is a test done during pregnancy. Amniotic fluid that surrounds your baby has cells and other substances that can give clues about the health of your fetus. A small amount of this fluid is taken out and tested.
This test is most often done when you are 15 to 20 weeks pregnant. But it can be done later in pregnancy.
Why is amniocentesis done?
This test can look for genetic problems, such as Down syndrome or neural tube defects like spina bifida.
You may want to have this test because:
- You are concerned about your baby because of your age. As you get older, you have a greater chance of having a baby with a genetic condition.
- You've had a baby with a genetic condition or neural tube defect.
- You or your partner has a family history of a genetic condition.
- You had a result from a screening test that was not normal.
This test may also be done to see if the amniotic fluid is infected.
How is amniocentesis done?
- You may be asked to empty your bladder.
- You will lie on your back on an exam table.
- Your belly will be cleaned with an antiseptic solution.
- You'll have gel rubbed on your belly. The gel works with the ultrasound device. Ultrasound makes a picture of your baby. It helps the doctor guide the needle through your belly to collect cells from the amniotic fluid.
- Your doctor will gently put a thin needle through your belly and into your uterus to take out a small amount of amniotic fluid.
How do you prepare for amniocentesis?
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.
What do the results of amniocentesis mean?
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) 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.
©2011-2026 Healthwise, Incorporated