Nonstress Test (NST)
The nonstress test (NST) measures the fetal heart rate as the fetus moves. When the fetus is moving around, its heart typically beats faster. During the NST, a belt with transducers is placed around the pregnant woman's waist for 20-40 minutes. Doppler ultrasound is used to measure the fetus' heart rate patterns, and a record is made on graph paper.
When the fetus is asleep or resting, it may not move for a short period of time—sometimes as long as 40 minutes. The healthcare provider may try to wake the fetus by having you eat or drink something, or by using sound.
Who Should Get This Test?
Your healthcare provider may recommend this test, as well as other tests, 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 at risk include:
- High blood pressure
- Too much or too little amniotic fluid
- Kidney disease
- Heart disease
- Post-term pregnancy
- Multiple pregnancy (two or more fetuses)
The NST is not always accurate. Sometimes the test suggests a problem even when the fetus is healthy. If there is no change in fetal heart rate in response to fetal movement, your healthcare provider may want to try another test to confirm the NST test results.
Your healthcare provider may suggest other tests so that he or she can gather important information about the health of your fetus. A problematic test result often suggests that you need special care. It does not necessarily mean that your fetus is in trouble. Your healthcare provider will be able to answer questions and discuss any concerns you have about monitoring.
American College of Obstetricians and Gynecologists
National Women's Health Information Center
Last reviewed July 2007 by Ganson Purcell Jr., MD, FACOG, FACPE
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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