What is the most likely sign of fetal acidemia?

Fetal acidemia refers to a state of metabolic or respiratory acidosis in the fetus, often due to hypoxia or other underlying conditions affecting oxygen delivery. Decreased fetal tone is a key indicator of fetal distress, suggesting that the fetus is experiencing compromised oxygenation. This decreased tone is frequently the result of a reduced ability to maintain normal muscle activity, which can occur when the fetus is under stress, leading to acidemia.

In the context of fetal monitoring, decreased tone typically presents as less active or hypotonic movements, which signals to healthcare providers that the fetus may not be receiving adequate oxygen. This is particularly important to recognize during labor and delivery to prompt further evaluation and potential intervention.

The other options reflect physiological responses that do not typically signal fetal acidemia. For instance, increased fetal heart rate variability is usually a reassuring sign, indicating adequate oxygenation. High fetal blood pressure is not a commonly assessed parameter in this context, and prolonged fetal movement may suggest a well-oxygenated state rather than distress. Thus, decreased fetal tone is the most appropriate indication of potential fetal acidemia that warrants attention.