What is defined as moderate variability in fetal heart tracing?

Moderate variability in fetal heart tracing refers to fluctuations in the fetal heart rate that fall within a specific range, indicating a healthy fetal response to environmental changes. The correct definition of moderate variability is an amplitude between 6 to 25 beats per minute (bpm).

This variability reflects the interplay of the fetal autonomic nervous system, particularly the sympathetic and parasympathetic systems, and is a sign of a well-oxygenated fetus. It suggests that the fetus is able to respond appropriately to stimuli, indicating normal cardiac health and well-being.

Variability outside this range, such as an amplitude of 0 bpm, would indicate absent variability—an important sign of potential fetal distress or hypoxia. An amplitude of 5 bpm does not meet the threshold for moderate variability and is considered minimal variability, which could suggest similar concerns. An amplitude greater than 25 bpm is classified as marked variability, which might also warrant further assessment. Thus, understanding the spectrum of variability is crucial in interpreting fetal heart tracings and making appropriate clinical decisions.