# Non-Stress Test (NST)

Source: https://www.pregnancypowerhour.com/tests/non-stress-test
Last updated: 2026-07-01

> The Non-Stress Test (NST) is a late-pregnancy assessment that monitors your baby's heart rate in response to their movements, offering insights into their well-being.

The Non-Stress Test (NST) is a gentle way to check on your baby's health in the later stages of pregnancy, particularly when there's a need for closer observation. This test focuses on how your baby's heart rate responds when they move, providing a snapshot of their current well-being.

## What it is

An NST is essentially a period of external fetal heart rate monitoring. During the test, two sensors are placed on your abdomen: one to track your baby's heart rate and another to detect uterine contractions. The goal is to observe your baby's heart rate patterns over a period, typically 20 to 40 minutes. This helps your care team understand how your baby is doing inside the womb, especially concerning their oxygen supply and overall responsiveness. It's a non-invasive procedure, meaning there are no needles or internal examinations involved.

## When and how it happens

NSTs are generally performed in the third trimester, usually starting around week 32, though they can be indicated from week 28 onward. It's important to know that routine NSTs are not recommended for low-risk pregnancies. Instead, they are typically indicated for pregnancies identified as high-risk. This might include situations such as gestational diabetes (which may have been diagnosed after a [Glucose Tolerance Test (3-hour)](/tests/glucose-tolerance-test)), high blood pressure, concerns about your baby's growth (like Intrauterine Growth Restriction, or IUGR), if you've gone past your due date, if you've noticed decreased fetal movement, or if there's a history of prior stillbirth. Your provider will help you understand if an NST is a helpful tool for your specific circumstances. During the test, you'll typically recline comfortably while the monitors are in place, and you might be asked to note when you feel your baby move.

## What the results mean

When your baby's heart rate shows two or more accelerations (increases of at least 15 beats per minute above their baseline, lasting 15 seconds or longer) within a 20-minute window, the NST is considered "reactive." This is generally a reassuring sign, indicating your baby is well-oxygenated and responsive. If the NST is "non-reactive," it simply means these specific heart rate accelerations weren't observed within the initial timeframe. A non-reactive result doesn't automatically mean there's a problem. Babies, like adults, have sleep cycles, and your baby might just be resting. In these cases, the monitoring might be extended, or your care team might use vibroacoustic stimulation (a gentle sound or vibration) to encourage your baby to wake up and move. Often, a non-reactive NST is followed by further assessment, such as a [Biophysical Profile (BPP)](/tests/biophysical-profile) ultrasound, which offers a more comprehensive look at your baby's well-being, or sometimes an [Umbilical Artery Doppler](/tests/umbilical-artery-doppler) to assess blood flow. Remember, your care provider is your best resource for understanding your specific health situation and test results.

## Questions worth asking

This is your pregnancy, and you get to decide what feels right for you and your baby. Asking questions is a powerful way to gain clarity and make informed decisions. One option might be to ask your provider about the specific reasons an NST is being recommended for you, and what alternative monitoring options, if any, might be available. Understanding the 'why' behind any test can bring you a lot of peace of mind.