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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, two elastic belts will be placed around the mother's stomach. Each belt will hold a special sensor. One sensor measure the fetus's heart rate. The second sensor will measure contractions in the uterus. The test generally last 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—sometimes as long as 40 minutes. 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:
- High blood pressure
- Too much or too little amniotic fluid
- Kidney disease
- Heart disease
- Multiple pregnancy (two or more fetuses)
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
National Women's Health Information Center
The Society of Obstetricians and Gynaecologists of Canada
Women's Health Matters
Complicated Pregnancy. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed/what.php. Updated November 30, 2012. Accessed December 12, 2012.
Fetal nonstress test (NST). American Pregnancy Association website. Available at: http://www.americanpregnancy.org/prenataltesting/non-stresstest.html. Updated March 2006. Accessed December 2, 2010.
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. United States Department of Health and Human Services Women's Health website. Available at: http://womenshealth.gov/pregnancy/you-are-pregnant/prenatal-care-tests.html. Available September 27, 2012. Accessed December 12, 2012.
Screening and Monitoring During Pregnancy. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed/what.php. Updated November 28, 2012. Accessed December 12, 2012.
- Reviewer: Brian Randall, MD
- Review Date: 12/2012
- Update Date: 12/12/2012