Prenatal tests help evaluate the well-being of the unborn baby (fetus). Thanks to these tests, possible problems in the developing baby can be detected in the early period. With these tests, which help to understand the general condition of the baby, the baby is intervened when necessary. Thus, it is aimed for the baby to complete its development in the mother's womb in a healthy way. In cases where there is a risk for the baby to remain in the mother's womb, the option of premature birth may come to the fore. One of the most frequently used tests among prenatal tests is the Non-Stress Test (NST).
What is NST?
Non-Stress test, namely NST, is a prenatal (prenatal) test used to check the health of the baby. This test monitors the baby's heartbeat. With the NST device, the baby's heartbeat is recorded when he moves or is at rest. In this way, it is checked whether the baby can increase the heart rate in response to body movements. Normally, just like children and adults, babies' heart rate should increase with movement. If the baby's heart rate does not increase when he moves, it can be thought that the baby is without oxygen. In order to perform NST, pregnancy must have entered the third trimester. NST test is usually done after 32 weeks, but 26-28 in high-risk pregnancies. It can also be done in weeks.
Who is NST for?
It may not be necessary for every pregnant woman to have an NST procedure. However, especially in high-risk pregnancies, regular NST procedure may be beneficial in order to closely monitor the health of the baby. Conditions that may require NST after entering the 3rd trimester of pregnancy:
- Multiple pregnancy condition that can cause various complications
- Mother's medical condition such as Type 1 diabetes, chronic heart disease or high blood pressure during pregnancy discomfort
- Two weeks delay from the planned date of birth
- Complications of the mother in previous pregnancies
- In case of slowdown in the baby's movements in the womb or a possible developmental disorder
- In the presence of blood incompatibility
- A decrease in amniotic fluid (oligohydramnios) can be listed as.
How to NST?
NST is a fairly easy test. Questions like 'What should be done before taking NST?' may be asked frequently by expectant mothers. Pregnant women do not need to do an additional procedure before NST.
Blood pressure of the expectant mother is measured before the NST procedure. The blood pressure measurement may be repeated several times during the NST procedure. After the blood pressure measurement, the expectant mother is asked to lie on the examination table. Afterwards, a special gel is applied to the belly of the expectant mother. A piece of the NST device is placed on the gel. Thanks to this piece, the baby's heartbeat is monitored during the procedure. In order to observe the contractions in the uterus, a device is placed on the uterus. Thanks to these two parts, the baby's heartbeat and movements in the uterus are recorded.
The subject of 'How long does NST take?' may differ from person to person. If the baby is active, the NST is done in just 20 minutes, while it takes longer to do the NST if the baby is inactive, asleep. If the unborn baby is asleep, it may be necessary to wake the baby to complete the NST procedure. For this, it may be useful to bring an audio device closer to the mother's womb or for the expectant mother to eat and drink something.
NST measurement results in pregnancy can be accessed immediately after the procedure. Therefore, there is no need to wait for results after the procedure. NST can also be used for tracking pain and contractions. Questions such as 'What should be the pain value in NST, what is the pain limit in NST?' are frequently encountered. NST contractions of at least 3 regular and greater than 40 mmHg for 20 minutes indicate the onset of labor.
How to Evaluate NST Result?
Based on NST values, two different results may occur:
Reagent: In NST performed before 32 weeks; The result is reactive if the baby's heart rate accelerates at least 2 times during the 20-minute interval and each acceleration takes at least 10 seconds. Normal NST values in the test performed after 32 weeks; the baby's heart rate is accelerating at least 2 times in every 20-minute interval compared to its normal state and this acceleration takes at least 15 seconds. if it falls below; The NST result is non-reactive. The nonreactive result may be seen because the baby is inactive or asleep.
NST time may be slightly extended to obtain a reactive test result. If the reactive result criteria are met within the extended period, it is decided that the baby's heartbeat is normal. However, if the NST procedure is continued for 40 minutes and the result is still nonreactive, the doctor may order different prenatal tests to check the baby's health. These tests are:
Biophysical Profile: Biophysical profile; It is a method in which the baby's breathing, movements, muscle tone and the amount of amniotic fluid in it are shown and interpreted by ultrasound. The biophysical profile is usually evaluated together with the NST results and gives information about the health status of the baby. The features of the baby with ultrasound and the NST results are evaluated out of 10. These scores are; rhythmic breathing of the baby is awarded 2 points, movement 2 points, muscle tone 2 points, and sufficient amniotic fluid 2 points.
In case the NST results are at the desired level, 2 more points are added. Babies with a biophysical profile of 10 points are considered healthy. With these results, it is recommended that the expectant mother continue her routine controls. Infants with a biophysical score of 8 may require further investigations. In cases where the score is 6 or less; The birth decision can be made by taking into account the factors such as the week of pregnancy and the health of the expectant mother.
Contraction Stress Test (CST): The contraction stress test can be thought of as the NST performed during uterine contractions. In CST, contraction of the uterus is created by stimulating the nipple or giving a stimulant substance. With this process, a kind of birth simulation is prepared for the baby. Uterine contractions are set to be three times in 10 minutes, and the baby's heartbeat is monitored during these contractions. If the baby is healthy, there is no problem during this procedure. However, if the baby will not be able to bear the birth, a decrease in heart rate is observed during contractions. Babies with a decrease in heart rate as a result of CST should be delivered by cesarean section, not by normal (vaginal) delivery.
NST interpretation is an application that should be done by experts in the field. . Doctors results; It evaluates by considering many parameters such as gestational week, general health status of mother and baby, conditions that may cause complications in pregnancy. A nonreactive NST result may not mean that the baby is unhealthy. As with any test, false results may be encountered in NST. As a result of NST and other tests, a situation such as premature birth may occur in terms of the health of the baby. In such a situation, the doctor evaluates the advantages and disadvantages of preterm birth together and explains all the possibilities to the family. With the joint decision of the family and the doctor, it is decided to continue the pregnancy or to give birth. Today, thanks to advanced newborn care, there is a significant reduction in complications related to preterm birth.
With the developing technology, it has become possible to evaluate the health status of the baby with prenatal tests. Prenatal tests allow early detection of a possible problem in the baby and immediate intervention for the problem. For this reason, it is very important for expectant mothers to have the necessary prenatal tests. It would be beneficial to prefer a well-equipped health center in terms of performing and evaluating prenatal tests and the necessity of a possible emergency response as a result of the test.
You can ask the expert team of Group Florence Nightingale Hospitals about the issues you are wondering about NST, and you can ask for suggestions regarding your question. You can use the contact form on our website to reach us.
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