The baseline fetal heart rate decreases with gestational age as a result of an increase...

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

As gestation advances:

Vagal (parasympathetic) control increases,

Sympathetic dominance decreases,

Resulting in a lower baseline heart rate.

NCC physiology teaching:

“Baseline FHR decreases with advancing gestational age due to maturation and increasing parasympathetic tone.”

Why the others are incorrect:

Catecholamines increase heart rate, not decrease it.

Intrinsic ventricular rate does not change significantly with gestational age.

Thus, the correct physiologic factor is increased parasympathetic tone.