What is an NST Test in Pregnancy?

A fetal non-stress test (NST) in pregnancy measures your contractions and baby’s heart rate. Find out why it’s done, who needs one, and what happens after the test.
As you get toward the end of pregnancy, it can feel like the doctor’s visits never stop. One of the many tests they might do to monitor your baby’s health in the third trimester is a fetal non-stress test (also called an NST test). What is an NST? Who needs one? And what do the results mean? Read on to find out everything you need to know about an NST test in pregnancy.
In this article: 📝

• What is NST in pregnancy?
• How long does a non-stress test usually take?
• What are they looking for during NST?
• What happens if you fail a non-stress test during pregnancy?
• Does everyone get a non-stress test during pregnancy?
• Why would a pregnant woman need a non-stress test?
• How do I prepare for an NST test?
• What should I eat before NST?
• Do Braxton Hicks show up on NST?
• Is an NST test painful?
• Can NST induce labor?
• NST in pregnancy: the bottom line

What is NST in pregnancy?

A non-stress test in pregnancy is a test to measure your baby’s heart rate and movement. It’s called “non-stress” because nothing is done to bother your baby or put them at risk. It’s noninvasive (no needles or incisions) and completely safe. You simply recline on a table or chair with two monitors strapped to your belly to measure your contractions and the baby’s heartbeat. You might also have a button to push whenever you feel the baby move.

How long does a non-stress test usually take?

Your doctor will take a look at the printout from the two monitors after 20 minutes. If they need more information at that point, you might have to stay on the monitor longer, sometimes up to 60 minutes total.

What are they looking for during NST?

An NST in pregnancy is done to test your baby’s heart rate and movement to make sure they’re still thriving and active in the womb. Your doctor will want to see if your baby is reactive (good!) or non-reactive (needs further testing). Reactive means that your baby’s heart rate has:

• Sped up at least 15 beats per minute over their resting rate
  
  
• For at least 15 seconds
  
  
• At least twice during the initial 20 minute test.

If you’re less than 32 weeks pregnant, the 15’s become 10’s — 10 beats per minute faster for 10 seconds. If your baby’s heart rate does meet those criteria, then the test is non-reactive. No need to worry just yet. It’s possible your baby is sleeping! At this point, your doctor might give you some ice water or a sugar drink or snack, or maybe even clap loudly near your belly to wake up your baby. (Yes, it works!) They’ll then continue the test for another 20-40 minutes to see if your baby’s heart rate can meet the 15 x 15 x 2 criteria.

What happens if you fail a non-stress test during pregnancy?

First, don’t think of this in terms of “failure.” This test is all about taking measures to protect the health of your baby. The results will allow your doctor to do so. If you’ve been on the monitors for between 40 and 60 minutes without enough movement from the baby, your doctor will likely recommend further tests to ensure the baby is okay. They might have you do a special ultrasound called a fetal biophysical profile — this is a test that combines a nonstress test with an ultrasound. This ultrasound measures fetal movement, fetal breathing, fetal tone (quick, jerky movements, like extending a leg), and amniotic fluid volume. Your doctor might also recommend a pregnancy stress test (aka contraction stress test). This test monitors how well your baby responds to labor contractions. It’s similar to the non-stress test, but you’ll be given pitocin (a synthetic form of the hormone oxytocin) to get some contractions going — these contractions are similar to labor, but don’t worry, they won’t induce it! After one or both of these tests, your doctor might decide that your baby is doing well and you can continue with your pregnancy, perhaps with further monitoring in a few days or weeks. But if they’re not satisfied with the results of these tests, they might recommend an induction or an emergency c-section. So if you’re going in for a biophysical or a contraction stress test, it’s a good idea to let your partner or a friend know, just in case you end up being admitted to the hospital for delivery.

Does everyone get a non-stress test during pregnancy?

No, not everyone gets a non-stress test during pregnancy. You’ll only get one for specific reasons, like going over your due date, or having a high risk pregnancy. Let’s take a look at some reasons why you might get an NST:

Why would a pregnant woman need a non-stress test?

Here are some of the situations where your doctor might recommend an NST during pregnancy:

• You have a health condition that might affect your pregnancy, including pre-existing diabetes, gestational diabetes, heart disease, or preeclampsia.
  
  
• There are growth concerns, especially if your baby appears too small.
  
  
• Your baby seems less active to you.
  
  
• There is too much or too little amniotic fluid.
  
  
• You’re past your due date.
  
  
• You’ve experienced a stillbirth in a previous pregnancy.
  
  
• You’re pregnant with multiples.
  
  
• A birth difference was detected on an earlier ultrasound and needs to be monitored.
  
  
• You’ve had an external cephalic version ( a maneuver that is done to help deliver a baby that is positioned to come out bottom or head first) or third-trimester amniocentesis (where a sample of amniotic fluid is sent for testing) and your doctor wants to make sure baby’s doing well.

Here are some other questions you might have about a non-stress test during pregnancy:

How do I prepare for an NST test?

It’s a good idea to visit the bathroom beforehand since you might be sitting for a while. It’s also ideal to wear a comfortable shirt that you can pull up easily, so the doctor can put the monitors on your belly.

What should I eat before NST?

It can help to eat or drink something before the test. Food and drink stimulate baby to move, which is what you want during the NST. Don’t worry if you didn’t bring any food or drink with you. If your baby isn’t moving enough during the initial 20 minutes, your doctor will likely have ice water or juice on hand to help them perk up.

Do Braxton Hicks show up on NST?

Yes, it’s possible for Braxton Hicks contractions to show up on the contraction monitor during an NST. The monitor will pick up contractions even if you can’t feel them or don’t know you’re having them.

Is an NST test painful?

No, an NST test during pregnancy is not painful at all. You’re simply reclining on a chair or table with monitors on your belly.

Can NST induce labor?

An NST test itself cannot induce labor. But it’s possible that your doctor might want to induce labor after getting the results from the test. And if you end up getting a stress test — where the doctor starts contractions to test your baby’s reaction — this might end up kicking you into labor.

NST in pregnancy: the bottom line

If your doctor has ordered a non-stress test during pregnancy, there’s no need to worry. It’s a common test, and it’s very likely that you will get through it without too many bumps in the road.
If you have any other questions about this test, it’s always okay to contact your healthcare provider — that’s what they’re there for. We know all these tests and doctor visits at the end of pregnancy can be nerve-wracking. You don’t have to do it alone! Check out the Peanut community for more support. Good luck, mama-to-be!