What commonly causes sudden fetal bradycardia during the second stage of labor?

The correct answer highlights the role of a vagal response during fetal descent as a common trigger for sudden fetal bradycardia in the second stage of labor. As the fetus descends through the birth canal, it can stimulate the vagus nerve, which is responsible for regulating heart rate. This stimulation often occurs when the fetal head exerts pressure on the cervix, leading to a transient decrease in fetal heart rate, known as bradycardia. This response is typically physiological and resolves as the labor progresses.

Vagal responses are a normal physiological mechanism that can happen during labor, particularly when the fetus is making significant movement through the birth canal. Understanding this is important for midwives and healthcare professionals, as it can help differentiate between a benign reaction and a situation requiring further intervention. The transient nature of this bradycardia is usually a result of the normal process of labor rather than indicating a pathological condition.

Other potential causes of fetal heart rate changes during labor, like maternal hypotension or complications such as placental abruption or preeclampsia, may lead to sustained or severe fetal bradycardia, but the vagal response during descent is a common and often benign explanation specifically for sudden bradycardia in the second stage