A
non stress test is a
prenatal medical test, which simply matches changes in the fetus's
heart rate with
fetal movement. The heart rate should change in predicable ways (it should increase) with fetal movement. If it doesn't it may be a sign of fetal stress. A sleeping fetus may be stimulated to move with a gentle nudge or vibration or a high sugar drink taken by the mother but other than that no interventions are done as part of the test so it carries no
risk of inducing labor. This is why it is called a NON stress test as contrasted with stress test in which contractions are actually induced.
A non stress test is typically done if there is some concern about the fetus or the pregnancy as part of the decision making process about the risk benefit ratio of inducing labor. It is not valid in early pregnancy and is typically done in the last month or if mother has gone beyound her EDC (
expected date of confinement) or "due date", a
notoriously vague concept at best.