What effect does the parasympathetic nervous system have on the fetal heart rate?

The parasympathetic nervous system, primarily through the action of the vagus nerve, influences the fetal heart rate by generally promoting a decrease in heart rate. This effect is achieved by slowing down the heart, which can lead to a bradycardic response in the fetus. During situations where the fetal body detects stimulation, such as during periods of rest or when the fetus is in a state of calm, the parasympathetic nervous system becomes more active, enhancing vagal tone and resulting in a slower heart rate.

In contrast, the sympathetic nervous system tends to increase the heart rate in response to stress or stimulation. Therefore, the interaction between these two branches of the autonomic nervous system is vital in maintaining homeostasis within the fetal environment, with the parasympathetic system playing a crucial role in modulating heart activity in the opposite direction.