What is NST ultrasound and what is its use?

NST (Non-Stress Test) ultrasound is one of the prenatal tests that assesses the well-being of the fetus. This test is usually performed in the third trimester of pregnancy, particularly in the weeks close to delivery, to ensure that the fetus is growing well in the mother’s womb and is not suffering from problems such as oxygen deficiency (hypoxia) or growth disorders.

Purpose of the NST Ultrasound

The main purpose of this test is to evaluate the fetal heart rate in response to its natural movements. Specifically, the NST checks whether the fetal heart rate increases with movement, which is an indicator of fetal health and adequate blood flow. If the fetus’s reaction to movement is not normal, further evaluation may be required.

Stages of the NST Ultrasound

This test is painless, requires no special preparation, and is performed as follows:

• Mother’s Preparation: The mother is positioned comfortably (sitting or semi-reclining).

• Equipment Setup: Two probes are placed on the mother’s abdomen; one to record the fetal heart rate and the other to record uterine contractions. These probes are secured to the mother’s abdomen with elastic belts.

• Recording Results: The machine records the fetal heart rate and its movements for about 20 to 40 minutes. If the fetus is not moving, the mother may be asked to drink some water or gently touch her abdomen to encourage movement.

Results of the NST Ultrasound

The results of this test are reported in two ways:

• Reactive: If the fetal heart rate increases with its movements, it indicates that the fetus is in good health.

• Non-Reactive: If the fetal heart rate does not react to its movements, it is a sign that the fetus may have problems. Further investigations, such as a Biophysical Profile (BPP) or Doppler ultrasound, are usually needed.

Applications of the NST Ultrasound

• Assessing Fetal Health in High-Risk Pregnancies: This test is regularly recommended for mothers with conditions such as diabetes or high blood pressure, or those at risk of preterm delivery.

• Investigating Fetal Growth Problems: If there are issues with fetal growth or suspicion of oxygen deficiency, the NST can help diagnose these problems.

• Ensuring Fetal Well-Being After Prolonged Labor: This test can help doctors ensure the baby’s health after going through prolonged stages of labor.

Advantages and Limitations of the NST Ultrasound

• Advantages: This test is non-invasive and painless, requires little time, and provides important information about fetal health.

• Limitations: In cases where a non-reactive result is obtained, it may not indicate a specific problem—the fetus could simply be asleep—therefore requiring additional tests.

Summary

The NST ultrasound is a safe, non-invasive, and accurate method for assessing fetal health in the third trimester of pregnancy. This test provides assurance to the mother and doctor that the fetal condition is normal and that adequate blood flow and oxygenation are occurring. In cases where the test result is non-reactive, the doctor may use complementary methods for a more accurate assessment to make appropriate decisions for pregnancy care.

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