Which is the earliest indicator of fetal compromise?

The Non-Stress Test (NST) is considered the earliest indicator of fetal compromise due to its ability to assess the fetal heart rate in response to fetal movements. This test evaluates the autonomic nervous system's regulation of the heart rate, which can offer immediate insights into the fetus's well-being. In a healthy fetus, there should be an increase in heart rate with movements, indicating an adequate response to stimuli and overall good health.

An abnormal NST, such as a non-reactive test where there are insufficient accelerations in fetal heart rate, can suggest potential fetal distress or placental insufficiency. This makes the NST a valuable tool in antenatal testing, allowing for early recognition of problems and potential intervention.

While indicators like fetal movements, fetal tone, and fetal breathing also provide important information about fetal health, they are generally less direct in assessing immediate compromise than the NST. Fetal movements can vary widely and are subject to maternal perception, while fetal tone and breathing assessments, often part of biophysical profiles, typically provide additional information but might not detect compromise as rapidly as an NST.