What does a greater than or equal to 25 bpm amplitude range in FHR variability indicate?

A greater than or equal to 25 beats per minute (bpm) amplitude range in fetal heart rate (FHR) variability indicates marked variability. This level of variability suggests that the fetal central nervous system is functioning appropriately and that the fetus is well-oxygenated. It reflects a healthy response to stimuli and indicates an active fetus.

In this context, FHR variability is an essential factor in assessing fetal well-being. Marked variability is typically associated with a robust autonomic nervous system, where the increment of 25 bpm or more signifies the fetus's ability to respond to changes in the intrauterine environment effectively. This is often viewed as a positive sign during fetal monitoring, indicating that the fetus is likely in good health and able to regulate its heart rate in response to various conditions.