A nonstress test during pregnancy looks at your baby’s heart rate and how it responds to movement.
In most cases, a baby’s heart rate will increase with movement.
This simple, painless screening test can’t diagnose conditions, but it’s often used in the third trimester to check on the baby's well-being.
Why is a nonstress test performed?
A nonstress test is performed for a variety of reasons with one of the most frequent ones being an expectant mother who hasn’t felt her baby kick or move for a while.
The prenatal screening is typically only done in the third trimester because that’s when you feel the baby move much more regularly.
Reasons a stress-test might be recommended include:
- Your pregnancy has gone two weeks past your due date
- Your baby is moving less than usual
- Your baby is measuring small
- You’re carrying multiple babies
- You have an underlying medical condition, like type 1 diabetes or high blood pressure
- You have low amniotic fluid
- You’ve had a stillborn baby or pregnancy complications in the past
Alternatively, your doctor may recommend a biophysical profile test.
Risks of a nonstress test
A nonstress test is named that because it doesn’t put any stress on or interfere with the baby. There are no known risks.
If the fear of the test causes you anxiety, remember that a nonstress test is simply a tool and more tests are needed to make a diagnosis.
What happens during a nonstress test?
A nonstress test is typically performed in a doctor’s office.
You’ll lie down on your back, and we’ll place a belt with a sensor around your belly to measure the fetal heart rate. This is similar to the monitoring that you will receive in labor.
Then, you’ll be asked to keep track of the baby’s movements. Sometimes this involves clicking a buzzer-like button.
The test typically lasts about 20 minutes but might take up to 40 minutes if your baby is less active.
Results of a nonstress test
It’s important to remember this test is only a screening tool where results aren’t always able to predict outcomes, whether good or bad.
Results of a nonstress test should be available immediately and they’re categorized as either reactive (normal) or nonreactive.
A reactive nonstress test means:
- Between 28 and 32 weeks, results are normal if your baby’s heartbeat rises to a certain amount twice for 10 seconds over 20 minutes.
- After 32 weeks, results are normal if your baby’s heartbeat rises a certain amount twice for 15 seconds over 20 minutes.
Sometimes, the test will be extended to 40 minutes. It doesn’t matter how long within that window it takes the baby to reach the criteria for the results to be considered normal.
A nonreactive nonstress test means:
We didn’t see a rise in heart rate when your baby moved. If this is the case, we might suggest another prenatal test to further examine what might be happening with your baby. These could include:
- A biophysical profile, which combines a nonstress test and ultrasound
- A contraction stress test, which looks at how the baby reacts to uterine contractions
Our Services
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Cell-free DNA test A simple blood test, this screens for genetic conditions, such as Down syndrome.
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Fetal echocardiogram A special ultrasound of your baby’s heart, this tool allows specialists to diagnose certain heart defects.
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Fetal kick counts Doing this exercise can provide a simple way to check on the baby during the later months of pregnancy.
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Group B Strep test This is a swab test to check for a bacteria strep infection during the later weeks of pregnancy.
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Nuchal translucency This ultrasound measures the collection of fluid under the baby’s skin at the back of the neck.
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Quad screening This blood test screens for open neural tube defects and other possible problems.