What is checked via non-stress testing (NST)?

Non-stress testing (NST) is a prenatal test that measures the fetal heart rate in response to fetal movements. The primary focus of NST is to assess the baseline fetal heart rate and its variability, as well as how it responds to movements. A reactive NST indicates a healthy fetal condition, where the heart rate shows an appropriate increase with fetal activity.

The baseline fetal heart rate provides crucial information about the well-being of the fetus. It reflects the direct response of the fetus to factors such as oxygenation and central nervous system development. Variations in the heart rate, particularly accelerations with movements, signal that the fetus is reacting well and suggests that the autonomic nervous system is functioning properly.

Other choices, while related to prenatal assessments, are not the primary focus of NST. Fetal movement is observed during the test but isn't the main parameter being checked; rather, it's the heart rate response to that movement which is the critical measurement. Fetal lung maturity and amniotic fluid index are assessed through different methods, such as amniocentesis and ultrasound, respectively. Therefore, the core objective of NST centers around evaluating the baseline fetal heart rate and its characteristics during this monitoring process.