When fetal arterial blood pressure increases, the baroreceptors send impulses to the vagus nerve resulting...

Comprehensive and Detailed Explanation From Exact Extract–Based NCC C-EFM References:

Fetal baroreceptors, located primarily in the carotid sinus and aortic arch, respond to increases in fetal arterial pressure. When activated, they stimulate the vagus nerve, causing:

Reflex parasympathetic activation

Decreased FHR (vagal slowing)

This is a well-established physiologic mechanism referenced throughout NCC’s physiology domain. NCC emphasizes that variable decelerations, especially short deep drops, can occur when transient increases in fetal blood pressure from cord compression activate these baroreceptors.

Option B, decreased PO₂, relates to chemoreceptor-mediated responses—not baroreceptors.

Option C, reflex tachycardia, is mediated by sympathetic activation and occurs when BP falls, not rises.

Thus, the correct physiologic response is A. Decreased heart rate.