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Non-Stress Tests (NST) in Pregnancy: Understanding This Health Check for Your Baby

Non-Stress Test (NST) Monitor Bedside


In the journey of pregnancy, there are numerous checkpoints designed to ensure both the mother and the baby are progressing well. The Non-Stress Test (NST) is one such tool used by healthcare providers to keep a close check on the baby's health. This non-invasive test provides valuable information about the baby's heartbeat and movement, contributing to a comprehensive assessment of fetal well-being.

But what exactly is it? This blog post "Non-Stress Tests (NST) in Pregnancy: Understanding This Health Check for Your Baby" dives deep into what they are and why they are used. Read below and let me know if you have any questions:


NST with a hand holding the Reactivity button

What is a Non-Stress Test (NST)?

The Non-Stress Test is a prenatal test used to monitor the baby’s heartbeat and check for signs of fetal distress. It's called a "non-stress" test because it places no stress on the baby. The test typically involves the mother wearing two belts around her abdomen: one to measure contractions and the other to track the baby's heart rate. The NST is generally performed after the 26th to 28th week of pregnancy, when the baby’s movements are well established.

Why is an NST Performed?

An NST is typically recommended in pregnancies where there's an increased risk of fetal distress. This might include situations where the mother has a medical condition such as diabetes or hypertension, the pregnancy is post-term, there's been decreased fetal movement, or the baby isn't growing as expected. However, an NST can also be used in routine check-ups to ensure everything is progressing as it should be.

What To Expect During an NST?

During an NST, the pregnant parent will be made to sit in a comfortable position, usually laying back, and two belts will be placed around their abdomen. One belt tracks the baby's heartbeat, while the other measures uterine contractions. For about 20-30 minutes, the healthcare provider will monitor the baby's heart rate, looking for an increase associated with the baby's movements, indicating a healthy, responsive baby. If the baby is sleepy or there is little activity, they may keep the parent on the NST longer (up to 3-4 hrs in some cases), hoping to get 20-30 minutes of fetal movement and activity. When the parent feels movement, they click a little button.

Understanding NST Results

The results of an NST can be classified as 'Reactive' or 'Non-Reactive'.

- A 'Reactive' result is what doctors are hoping for. It indicates that the baby's heart rate is increasing normally with its movements, which is a good sign of a healthy baby.

- A 'Non-Reactive' result doesn't necessarily mean something is wrong. It may simply mean the baby was asleep during the test or not moving much. If the results are 'Non-Reactive', the doctor may opt for a longer NST or use additional tests such as a Biophysical Profile (BPP) or an Ultrasound for further investigation.

Are NSTs Safe?

NST is a non-invasive and safe procedure. It doesn't pose any physical risk to either the mother or the baby. Some mothers might find the belts slightly uncomfortable, but it doesn't cause any harm. The primary objective is to provide a snapshot of the baby's well-being and to ensure that the pregnancy is progressing healthily.

When and How Often Should NSTs be Performed?

The timing and frequency of NSTs can vary depending on the specific circumstances of the pregnancy. In high-risk pregnancies, such as those with gestational diabetes or preeclampsia, NSTs may be recommended once or twice a week starting around the 32nd week of pregnancy. For pregnancies without complications, NSTs may be performed less frequently, such as once or twice a month during the third trimester.

Factors Monitored During an NST

During an NST, the healthcare provider closely monitors two main factors: the baby's heart rate and its movements. A healthy baby's heart rate should increase by a certain amount when it moves. This increase, known as an "acceleration," indicates that the baby is getting enough oxygen and nutrients. The healthcare provider also looks for a certain number of fetal movements within a specific timeframe.

Additional Tests in Conjunction with NST

In some cases, if the NST results are non-reactive or if there are other concerns, additional tests may be recommended to gather more information about the baby's well-being. One commonly used test is the Biophysical Profile (BPP), which combines the NST with an ultrasound evaluation of the baby's breathing, movement, muscle tone, and amniotic fluid levels. Another test that may be used is the Doppler ultrasound, which assesses blood flow in the umbilical cord and other key areas.

What If NST Results Raise Concerns?

If the NST results indicate any concerns, further evaluation and interventions may be necessary. The healthcare provider may recommend additional testing, such as a BPP or a contraction stress test (CST), to gather more information. They may also closely monitor the mother's blood pressure, perform blood tests, or consider an early delivery (induction) if the situation warrants it.

The Importance of Communication and Follow-up

It's crucial for expectant mothers to communicate openly with their healthcare provider throughout the pregnancy, especially if they notice any changes in their baby's movements or have concerns. If an NST is recommended, understanding the purpose and process of the test can help alleviate anxiety and ensure active participation in the monitoring process. Regular follow-up appointments and discussions with the healthcare provider are essential to address any questions or concerns and to adjust the monitoring plan as needed. Please also understand informed consent is at play here. If choices are being made or recommendations are happening, active participation is essential. Parents can consent, refuse, or request more information to make an informed choice. Read more on informed consent in my past blog post, here.


A TOCO on a mom's belly during an NST.

Non-Stress Tests (NSTs) play a vital role in monitoring the well-being of the baby during pregnancy, particularly in high-risk situations. This non-invasive procedure provides valuable information about the baby's heart rate and movements, offering insights into their health and development. By closely monitoring the baby's responses, healthcare providers can detect potential issues early and take appropriate actions to ensure the best outcome for both mother and baby. Always remember, every baby and every pregnancy is unique. Regular check-ups and tests like the NST are there to ensure that your baby's journey into the world is as safe and healthy as possible.

Have you had an NST before? What are your thoughts about it?


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