Short-term variability

Short-term variability (STV) is calculated as the difference between the average heart rate intervals recorded during the previous and subsequent periods of time equal to 4 seconds. Normally, this indicator is more than 5 ms. An STV value of less than 3 ms indicates the critical condition of the fetus, which requires urgent action to improve the condition of the fetus, or urgent delivery. If the STV value is from 3 ms to 5 ms, the fetal condition is suspicious and further thorough examinations of the pregnant woman by other methods and devices are required.