Which variability category indicates that the fetus is likely compromised?

The absence of variability in fetal heart rate is significant because it indicates a lack of responsiveness of the fetal heart rate to the fetal movement and environmental stimuli. In a healthy fetus, variability reflects the autonomic nervous system's regulation of heart rate, showing that the fetus is able to respond appropriately to stimuli such as movements, contractions, and changes in oxygen levels. When variability is absent, it may suggest that the fetus is experiencing some form of distress, such as hypoxia or acidemia, leading to compromised fetal well-being.

In contrast, marked variability suggests a well-oxygenated fetus with a healthy autonomic response, while moderate variability also indicates a stable condition. Minimal variability could be a cause for concern but does not necessarily imply compromise as strongly as the complete absence of variability does. Therefore, recognizing the absence of variability is critical in assessing fetal health and potential need for intervention.