Non-Stress Test

A non-stress test (NST) is an external antepartum fetal surveillance test. A Doppler transducer records the fetal heart rate (FHR), while a tocotransducer records uterine activity. No contraction is deliberately induced; the test asks how the fetal heart responds spontaneously to fetal movement. A healthy fetus with adequate oxygenation usually has bursts of movement accompanied by transient FHR accelerations. Those accelerations reflect intact autonomic nervous system function. Variability—the small, ongoing fluctuations around the baseline—also reflects fetal autonomic activity and oxygenation. The NST is therefore a screening test, not a diagnosis: a reactive tracing is reassuring at that time, but it does not guarantee continued fetal well-being or exclude every placental or fetal problem. An experienced nurse looks at the tracing as a pattern rather than counting accelerations in isolation. A normal baseline with moderate variability and movement-related rises is reassuring. A fetus that is quiet may simply be asleep, but persistent loss of variability, an abnormal baseline, or decelerations changes the priority from observation to assessment and escalation.