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Amniocentesis: About This Test


What is it?

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 this test 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 do you prepare for the test?

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

How is the test 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 does having amniocentesis feel?

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.

How long does the test take?

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

What happens after the test?

  • You may have mild cramps or vaginal spotting after the test. This should go away within a day.
  • You will probably be able to go home 15 to 30 minutes after the test.
  • Your doctor may ask you to avoid strenuous exercise, lifting anything heavy, and sex after the test. By the next day, you can do your normal activities, unless your doctor tells you not to.

When should you call for help?

Call your doctor, midwife, or nurse advice line now or seek immediate medical care if:

  • You have signs of infection at the place where the needle went in. These may include:
    • Increased pain, swelling, warmth, or redness.
    • Red streaks leading from the area.
    • Pus draining from the area.
    • A fever.
  • You have pain in your belly or pelvis.
  • You have vaginal bleeding.
  • You are cramping.
  • You notice fluid coming from your vagina.

Watch closely for changes in your health, and be sure to contact your doctor, midwife, or nurse advice line if you have any problems.

Follow-up care is a key part of your treatment and safety. Be sure to make and go to all appointments, and call your doctor or nurse advice line (811 in most provinces and territories) if you are having problems. It's also a good idea to keep a list of the medicines you take. Ask your doctor when you can expect to have your test results.

Where can you learn more?

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