All About Fetal Non-Stress Test (NST)
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NST is one of the words you will hear from your doctor frequently since the last pregnancy period is entered. In this article, we have compiled for you the things that are curious about NST, which is described as an examination that detects fetal movements and increases in heart rate as a sign of the fetus being healthy in the following weeks of pregnancy.
What is NST?
It is an examination that detects fetal movements and increases in heart rate as a sign of the fetus being healthy in the following weeks of pregnancy.
For what purpose and in what situations is it used during pregnancy? At what stage of pregnancy is NST needed?
It is used to determine the health of the fetus in the womb during pregnancy. NST examination is essential in monitoring the fetus’s health, especially in maternal diseases such as diabetes, high blood pressure, chronic kidney disease, goiter, high blood pressure during pregnancy, decreased fetal movements, growth retardation, decreased water and gestational age past 40 weeks.
It is usually started to be performed at 32 to 34 weeks. In the presence of risk factors related to pregnancy, such as the threat of preterm birth, it can be started earlier, such as the 26th gestational week. Regular NST pain values examination should be repeated after one week or two times a week. In case of deterioration of clinical findings, it is repeated regardless of the elapsed time.
How long does the NST procedure take?
The process takes 20 minutes. It can be applied for 40 minutes or longer, depending on the baby’s sleep cycles.
How is NST interpreted?
Increases in heart rate in NST are interpreted according to the gestational week. At least two increases in the NST above the 32nd gestational week. The heart rate rises above the average rate by 15 beats for at least 15 seconds and a maximum of 2 minutes and returns to the average rate is considered a regular NST examination.
Before the 32nd gestational week, at least two increases in the NST for 10 seconds. The heart rate goes above the average rate by ten beats and returns to the average rate is considered a regular NST examination.
What does the NST result tell us about the baby's health?
The result of NST pain values gives the change of heartbeat of the fetus according to the movements in the mother’s womb. It is also helpful in detecting uterine contractions in the mother and distinguishing whether or not actual labor has begun. It is essential to monitor the intensity and interval of contractions in the uterus regarding maternal and fetal health at the beginning and follow-up of labor.
Can the NST pain test be harmful to the baby or the mother? Is it Reliable?
The test does not cause any harm to the baby or the mother.
It is observed that the fetus is expected in 80% of the cases whose NST pain values are abnormal. Abnormal NST findings may be related to gestational age. Depending on the fetus’s development, NST is generally observed in 80% of the fetuses before the 28th gestational week. Normal NST finding in these weeks gives information that the fetus is healthy, as in advanced weeks of gestation.
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