Which fetal condition can lead to bradycardia due to head compression?

The phenomenon of bradycardia due to head compression during labor is strongly associated with vagal stimulation. When the fetal head encounters pressure, often during the descent through the birth canal, it can trigger the vagus nerve, which in turn slows the heart rate. This physiological response is a protective mechanism and can be particularly common during labor, especially in cases of prolonged or difficult labor.

In contrast, fetal hypoxia may lead to various heart rate patterns, including variable decelerations or tachycardia, rather than isolated bradycardia due to head compression. Hypotension primarily affects blood flow and perfusion rather than directly triggering the vagal response that would result from head compression. Meanwhile, fetal heart structural defects can lead to arrhythmias or other heart rate abnormalities, but they do not directly cause bradycardia resulting from vagal stimulation due to head compression. Thus, vagal stimulation is the primary mechanism by which head compression during labor can lead to fetal bradycardia.