Central and autonomic regulation of fetal heart rate: nonlinear analysis after vibroacoustic stimulation

Vibroacoustic stimulation is able to produce a fetal sensory response, which is mediated by the Central Nervous System (CNS). Despite the fetal heart rate variability is basically regulated by Autonomic Nervous System (ANS), some changes in the FHR appear as a direct consequence of the sensory stimulation. The paper proposes an analysis of FHR of 13 normal subjects based on nonlinear approaches. Detrended Fluctuation Analysis (DFA), Approximate Entropy and Poincare plots are able to evidence differences that can be attributed to fetal nervous system activity. In particular DFA decreases after stimulation confirming a reduction in the longterm correlation properties of FHR. The parallel, marked increase of ApEn indicates a regularity loss after the sensory stimuli. Nonlinear indexes seem able to describe complex interactions of different neural mechanisms which control the FHR.