What is a non stress test (NST)?
A non stress test (NST) measures the heart rate of the fetus in response to his/her own movements (usually after 28 weeks of pregnancy.) Healthy babies will respond with an increased heart rate during movements. The concept behind a NST is that adequate blood flow (and oxygen) is required for normal fetal activity and heart rate. When oxygen levels are low, due to problems with the placenta or umbilical cord, the fetus may not respond normally.
