Nonstress Test
Reviewed
Also called: fetal nonstress test, categoryDetailsList: [
A nonstress test (NST) is a safe and painless test given during pregnancy. The test measures the heart rate of your developing baby as the baby moves.
Specimen: not applicable
Why this test may be ordered
- Baby seems to be moving less than usual
- Pregnancy is overdue (42 weeks or beyond)
- High-risk pregnancy due to chronic conditions (e.g., high blood pressure, diabetes, heart disease, clotting disorder)
- Complications in a previous pregnancy
- Rh incompatibility (mother Rh-negative, baby Rh-positive) that may cause immune attack on baby's red blood cells
Preparation and collection
You don't need to do any special preparations for a nonstress test. However, your provider may ask you to go to the bathroom to empty your bladder before the test.
The test may be done in your provider's office or a hospital's prenatal area. Your provider will attach two belt-like devices around your abdomen. One will measure your baby's heartbeat. The other will record your contractions. The test usually lasts about 20 minutes to 30 minutes.
There is no risk to you or your baby from having a nonstress test.
Understanding results
Nonstress test results are given as one of the following: Reactive or Reassuring.
- Reactive (reassuring): This means your baby's heart rate increased two or more times during the testing period. Limitation: In most healthy babies, the heart rate, also known as the fetal heart rate, increases during movement. Next step: If you have questions about your results, talk to your provider.
- Nonreactive: This means your baby's heartbeat didn't increase when moving or the baby wasn't moving much. Limitation: A nonreactive result doesn't always mean your baby has a health problem. Your baby may have been asleep and not easily awoken. Nonreactive results may also be caused by certain medicines taken during pregnancy. Next step: But if the result was nonreactive, your provider will probably take more tests to find out if there is cause for concern.
- A nonreactive result does not always mean the baby has a health problem; the baby may have been asleep or certain medicines may affect the result.
- Additional testing (e.g., biophysical profile, contraction stress test) may be needed to clarify results.
What to do next
If your baby is found to be at risk, you may need treatment or monitoring, or to have labor induced if it is late enough in your pregnancy. If you have questions about your results, talk to your provider.
- What does my result mean for my baby's health?
- If my result was nonreactive, what additional tests might be needed?
- How often should I have this test during my pregnancy?
Evidence source
Source: U.S. National Library of Medicine (MedlinePlus). Practices and reference ranges may differ in your country.