What is the leading cause of poor variability in fetal heart rate?

Fetal hypoxia, or insufficient oxygen supply to the fetus, is the leading cause of poor variability in fetal heart rate. Variability refers to the fluctuation in the fetal heart rate that reflects the level of autonomic nervous system function and the well-being of the fetus. When a fetus is hypoxic, the body's compensatory mechanisms can become dysfunctional, leading to decreased heart rate variability. Healthy fetal heart rate patterns typically demonstrate a certain degree of variability, indicating that the fetus is reacting appropriately to internal and external stimuli.

In cases of fetal hypoxia, the fetus may not be able to maintain this normal heart rate variability, resulting in a more flat or decreased pattern. This is critical for practitioners to recognize, as it may indicate potential distress or an underlying problem that requires immediate intervention. Understanding the relationship between fetal heart rate variability and conditions like hypoxia is essential for monitoring fetal well-being during labor and delivery.

The other factors listed may have some impacts on fetal health but are not as directly correlated with reduced variability in fetal heart rate.