What does the nonstress test (NST) primarily measure?

The nonstress test (NST) primarily measures the fetal heart rate and assesses how it responds to the baby's movements. The primary objective of the NST is to determine the well-being of the fetus by evaluating its heart rate patterns. A normal NST shows that the fetal heart rate increases with movements, indicating that the fetus is receiving enough oxygen and is not in distress.

While fetal movement is also observed during an NST, the test specifically focuses on the relationship between heart rate accelerations and fetal movements to assess fetal health. Fetal breathing movements and maternal blood pressure are not assessed through this specific test, as they relate to different aspects of pregnancy monitoring. Hence, the nonstress test effectively provides reassurance about the fetus's condition by closely monitoring its heart rate trends in response to movement.