What is a Nonstress Test and Why is it Performed During Pregnancy?

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What is a Nonstress Test and Why is it Performed During Pregnancy?

pregnancyUpdated January 16, 2022

by Mandy Johnson

Prenatal Care Specialist


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Prenatal visits are essential throughout pregnancy, as they allow constant monitoring and care for your unborn baby. Such consultations involve a routine physical examination with your midwife or obstetrician. In most cases, you may be requested to undergo several prenatal tests. This may include a nonstress test, which may also be referred to as fetal heart rate monitoring.

A nonstress test is a common prenatal test that allows you to further check on the baby’s health. This test generally monitors the baby’s heart rate in response to its movements. Pregnant mothers often need nothing to worry about. No stress is placed on the fetus while the test is performed, as the name suggests.

Why It’s Done

By monitoring the baby’s heart rate and how it responds during movement, the healthcare team can gather essential information regarding their oxygen supply. Just like an adult’s, the baby’s heart rate normally beats faster during activity, especially later in pregnancy. The test will monitor heart rate variability in response to fetal movement.

Otherwise, the baby could be experiencing fetal hypoxia—a condition where they do not get adequate oxygen. With a nonstress test, your doctor will be able to decide whether there is a need to do further monitoring, testing, or intervention to prevent fetal death.

Who It’s For

Not all pregnant women may be required to undergo a nonstress test. Your doctor may still suggest it if you have certain complications throughout your pregnancy. These can include gestational diabetes, heart disease, preeclampsia, or a postdate pregnancy. A nonstress test can also be recommended if you have had an amniocentesis or diagnosed with low amniotic fluid.

Your baby needs to be at a certain weight, depending on his or her gestational age. If baby measures small and isn’t very active, then a nonstress test may be performed. It is also performed when you are past your due date, yet you haven’t gone into labor. Usually, the test is done during your third trimester of pregnancy, which is from week 28 onwards.

How it’s Performed

During a nonstress test, belts are strapped across the mother’s abdomen and connected to two different types of transducers—the Doppler to measure the baby’s heart rate and the toco transducer to measure the contractions. Toco transducers work by measuring the relative rate, strength, and uterine contractions duration. These are the same fetal monitors you will likely be hooked to during labor if you are planning a hospital birth.

The entire test measures the heart rate, movement, and reactivity of the fetal heart rate to movement. It will go on for about 20 to 30 minutes. In case the baby does not move, it does not immediately indicate a problem as he or she could be asleep. Your healthcare provider may use a small “buzzer” to alert the baby while the test is performed. You may also be encouraged to drink some juice or eat something sugary to prompt baby to move and get excited!

What the Results Mean

A reactive nonstress test result occurs when the baby’s heart rate rises normally during movement. This means that the baby is receiving adequate oxygen and blood flow.

Meanwhile, a non-reactive result means that the baby’s heart rate did not increase enough during a minimum number of movements within a 40-minute period, which may require further observation and more tests to further check on your baby’s health, such as a biophysical profile or a contraction stress test. In more serious cases, your doctor may recommend labor induction and early delivery, especially in the case of a non-reactive result during week 39 or a full-term pregnancy.

A nonstress test may be something you have not heard of until today. Make it a point to be on top of your prenatal consultations by discussing prenatal tests in-depth and what they might mean for you and your little one!


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