<P> The premise of the NST is that a well - oxygenated, non-acidemic fetus will spontaneously have temporary increases in the fetal heart rate (FHR). </P> <P> Vibroacoustic stimulation can wake the fetus, and is sometimes used to speed up the test or to facilitate further evaluation of a non-reactive nonstress test . </P> <P> A nonstress test can be classified as normal, atypical, or abnormal . A normal nonstress test will show a baseline fetal heart rate between 110 and 160 beats per minute with moderate variability (5 - to 25 - interbeat variability) and 2 qualifying accelerations in 20 minutes with no decelerations . </P> <P> Previous terminology: Reactive / non-reactive: </P>

How does a fetal non stress test work