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.
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 pressureDiabetesToo much or too little amniotic fluidKidney diseaseHeart diseaseMultiple 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.
Preboth M. ACOG Guidelines on Antepartum Fetal Surveillance. American College of Obstetricians and Gynecologists.
Am Fam Physician
Last reviewed December 2012 by Brian Randall, 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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