What effect does sympathetic nervous system stimulation have on fetal heart rate?

Sympathetic nervous system stimulation has a direct impact on the fetal heart rate by increasing it. This is due to the release of catecholamines, such as adrenaline, which enhance the contractility and rate of the heart by acting on beta-adrenergic receptors. When stimulated, the sympathetic nervous system prepares the body for 'fight or flight' responses, which in turn elevates the heart rate to supply more oxygen and nutrients to vital organs, including the developing fetus.

In contrast, parasympathetic activity, mediated primarily through the vagus nerve, works to decrease heart rate. The stabilization of heart rate typically results from a balance between these two systems, but sympathetic activation clearly boosts the heart rate, which is particularly critical during labor and delivery when increased cardiac output can support fetal oxygenation. Hence, the correct answer highlights the physiological response of the fetal heart to sympathetic stimulation.