Abstract
Development of the foetal autonomic nervous system can be indirectly understood by looking at the changes in beat to beat variability in foetal heart rates. This study presents Tone-Entropy (T-E) analysis of foetal heart rate variability (HRV) at multiple lags (1–8) to understand the influence of gestational ages (early and late) on the development of the foetal autonomic nervous system (ANS). The analysis was based on foetal electrocardiograms (FECGs) of 46 healthy foetuses of 20–32 weeks (early group) and 22 foetuses of 35–41 weeks (late group). Tone represents sympatho-vagal balance and entropy the total autonomic activities. Results show that tone increases and entropy decreases at all lags for the late foetus group. On the other hand, tone decreases and entropy increases at lags 1–4 in the early foetus group. Increasing tone in late foetuses might represent significant maturation of sympathetic nervous systems because foetuses approaching to delivery period need increased sympathetic activity. T-E could be quantitative clinical index to determine the early foetuses from late ones on the basis of maturation of autonomic nervous system.
Highlights
Foetal well-being during pregnancy has been widely evaluated with fluctuations of foetal heart rate or foetal heart rate variability monitoring
The question this paper addressed was whether multi-lag T-E values of foetal heart rate variability (fHRV) can be used to correctly identify a foetus as early or late, which takes into consideration the influence an individual beat has on subsequent beats in the time series
We suggest that the present results of increasing tone of the late foetus group is an alternate expression of this increased sympathetic activity and decreasing entropy as a reduction of heart rate variability (HRV) because entropy represents the total acceleration-inhibition activity of the cardiac autonomic nervous system function and outcome
Summary
Foetal well-being during pregnancy has been widely evaluated with fluctuations of foetal heart rate or foetal heart rate variability (fHRV) monitoring. In gestation the foetal heart rate is predominately under the control of the sympathetic nervous system and arterial chemoreceptors [2]. There is an interplay between the sympathetic (acceleration) and parasympathetic (deceleration) nervous systems in the control of heart rate. These systems exert their control via the cerebral cortex, the medulla oblongata, the sympathetic ganglia and the vagus nerve. The interaction between these systems results in a difference in the beat-to-beat intervals resulting in variability of the foetal heart rate tracing.
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