A nonstress test (NST) is a noninvasive test that monitors your baby's heart rate to see how it responds as your baby moves. It's typically done after 28 weeks when your baby's heart-rate patterns are more regular.
Your provider may recommend an NST to check on your baby’s health in the following situations:
- You don't feel your baby moving as much.
- Your baby is measuring small for its gestational age.
- You have a high-risk pregnancy (due to high blood pressure, diabetes, previous pregnancy complications, etc.).
- You're carrying more than one baby (twins, triplets, etc.).
- You're past your due date.
You usually don't need to do anything special to prepare, though your provider may ask you to empty your bladder beforehand.
The test usually takes about 30 minutes but could take longer.
You'll lie on a reclined chair or exam table and wear elastic belts with sensors. If your baby isn’t moving, your provider may use a small buzzer or have you drink something sugary to encourage movement.
Your results will either be:
- Reactive, meaning your baby’s heart rate increased with movement at least 2 times in 20 minutes. This is a normal result.
- Nonreactive, meaning there was no increase in heart rate or movement.
A nonreactive result doesn't necessarily mean something is wrong, just that more information is needed. Your provider will recommend additional tests to understand the cause, which could be that your baby was asleep.
Understand why your provider may recommend a nonstress test, what to expect, and how to make sense of your results.
