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Fetal Nonstress Test (NST): Measuring Your Baby's Heartbeats

The nonstress test (NST) is a measurement of the heart rate of the fetus. It is a quick check to make sure the baby is in good health. During the NST, an elastic belt will be placed around the mother's stomach. It will hold a special sensor that will measure the fetus's heart rate. The test generally lasts for 20-30 minutes.

The doctor will want to get a heart measurement while your fetus is moving. When the fetus is moving around, the heart typically beats faster. If the fetus is asleep or resting, there may not be any movement for a short period of time. In this case, the doctor may try to wake the fetus by having you eat or drink something, or by using sound against the belly.

Who Should Get This Test?

Your doctor may recommend this test during the third trimester, if you have a medical condition that could put you at risk for having problems with your pregnancy. Examples of conditions that could put you or the baby at risk include:

You may also have an NST if:

  • You feel your baby is not moving as often as usual.
  • You are overdue.
  • There may be placenta problems.

The NST is not always accurate. Sometimes the test suggests a problem even when the fetus is healthy (known as a false-positive result). If there is no change in fetal heart rate in response to fetal movement, your doctor may want to try another test to confirm the NST test results.

Your doctor may also suggest other tests to gather important information about the health of your fetus. A problematic test result, such as no increase in the baby's heart rate with movement, may suggest that you need special care. It does not necessarily mean that your fetus is in trouble. Your doctor will be able to answer questions and discuss any concerns you have about monitoring.


American Congress of Obstetricians and Gynecologists

American Pregnancy Association


The Society of Obstetricians and Gynaecologists of Canada

Women's Health Matters

Fetal nonstress test (NST). American Pregnancy Association website. Available at: Updated March 2006. Accessed December 29, 2014.

Preboth M. ACOG Guidelines on Antepartum Fetal Surveillance. American College of Obstetricians and Gynecologists. Am Fam Physician 2000;62(5):1184.

Prenatal care and tests. Women's Health—US Department of Health and Human Services website. Available at: Available September 27, 2010. Accessed December 29, 2014.

Routine prenatal care. EBSCO DynaMed website. Available at: Updated December 29, 2014. Accessed December 29, 2014.

Last reviewed December 2014 by Michael Woods, MD

Please be aware that this information is provided to supplement the care provided by your physician. It is neither intended nor implied to be a substitute for professional medical advice. CALL YOUR HEALTHCARE PROVIDER IMMEDIATELY IF YOU THINK YOU MAY HAVE A MEDICAL EMERGENCY. Always seek the advice of your physician or other qualified health provider prior to starting any new treatment or with any questions you may have regarding a medical condition.

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