Nonstress test

Overview

A nonstress test is a common test used before birth to check on a baby's health. During a nonstress test, the baby's heart rate is watched to see how it responds to the baby's movements. The term "nonstress" means that nothing is done to put stress on the baby during the test.

A nonstress test is most reliable at 32 weeks of pregnancy or later, but it can be done sooner if needed. Some nonstress test results might show that you and your baby need more checkups, testing or special care.

A nonstress test is done without surgery and won't physically harm you or your baby.

Why it's done

A nonstress test is used to look at a baby's health before birth. It can tell your health care provider if your baby is getting enough oxygen. The test checks your baby's heart rate and how it responds to movement. The test might show a need for further care or testing. Or it could show that the baby needs to be delivered.

Usually, a baby's heart beats faster during activity. However, health problems such as fetal hypoxia — when the baby doesn't get enough oxygen — can prevent the heart from beating faster during movement.

Your health care provider might recommend a nonstress test if you:

  • Are pregnant with more than one baby and have certain health problems.
  • Have a health issue during pregnancy, such as diabetes, heart disease or high blood pressure.
  • Are 41 weeks pregnant or later. This is called late-term or post-term pregnancy.
  • Had complications in a prior pregnancy.
  • Have a baby that isn't moving or growing in a typical way.
  • Are Rh sensitized. Rh sensitization can be a serious health issue. It happens when your blood and your baby's blood are not compatible.
  • Have low amniotic fluid — a condition called oligohydramnios.

Your health care provider might recommend having nonstress tests once or twice a week — and sometimes daily — depending on your health and your baby's health.

Risks

A nonstress test is done without surgery and has no physical risks for you or your baby. The test is called "nonstress" because there is no stress put on the baby during the exam.

While a nonstress test can bring relief about your baby's health, it may cause worry too. A nonstress test might suggest there is a problem when there isn't, which can lead to more testing. Also, good results don't always mean there won't be future issues.

Keep in mind that while a nonstress test is often done because of certain risks to you or your baby, it may not always be useful. That's because the test has not been shown to prevent pregnancy loss.

How you prepare

You don't usually need to do anything special before a nonstress test.

What you can expect

A nonstress test is usually done in your health care provider's office.

Before the procedure

Your blood pressure is taken before the nonstress test starts.

During the procedure

During the nonstress test, you'll lie on a reclining chair. You'll have your blood pressure taken at regular times during the test.

Your health care provider or a member of your health care team will place a sensor around your stomach area that measures your baby's heart rate.

A nonstress test often lasts 20 minutes. However, if your baby is not active or is asleep, you might need to continue the test for another 20 minutes or longer. This will allow time for your baby to wake up. It also helps make sure your test results are correct. Your health care provider might try to excite the baby by placing a noise-making device on your stomach.

After the procedure

After the nonstress test is done, your health care provider will discuss the results with you.

Results

Results of a nonstress test are either:

  • Reactive. If your nonstress test results are called reactive, it means they are considered to be reassuring. Before week 32 of pregnancy, results are reactive if your baby's heartbeat rises a certain amount at least twice for 10 seconds or more during the test. At week 32 of pregnancy or later, results are reactive if your baby's heartbeat rises a certain amount at least twice for 15 seconds or more during the test.
  • Nonreactive. If your baby's heartbeat doesn't rise as it should, the results are called nonreactive. Nonreactive results might happen because your baby was asleep or not moving during the test.

A reactive nonstress test is usually seen as a good sign by your health care provider. This is true even if your baby was asleep or not moving at first, and you needed more testing time. However, if the test results are nonreactive for 40 minutes or more, your health care provider will likely do another test to check your baby's health. For example:

  • Biophysical profile. A biophysical profile combines a nonstress test with a fetal ultrasound that tracks your baby's breathing, body movements, muscle tone and amniotic fluid level.
  • Contraction stress test. This test looks at how your baby's heart rate reacts when your uterus contracts. During a contraction stress test, if the uterus isn't contracting enough on its own, you may be given oxytocin in a vein or be asked to rub your nipples. This will help your uterus contract lightly.

Other reasons why a nonstress test may be nonreactive, other than your baby not moving or being asleep, include low oxygen and fetal brain or heart issues. Smoking or taking certain medicines also can cause a nonreactive stress test result.

Rarely, during a nonstress test, problems with a baby's heart rate are found that need more testing or treatment.

Talk to your health care provider about your nonstress test results. He or she can help explain what the results mean for you and your baby.

Last Updated Mar 22, 2023


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