Symbolic dynamics in cardiotocographic monitoring

Foetal heart rate variability is considered an important parameter, capable to highlight foetal reactivity and wellbeing. Many studies focused their attention on foetal heart rate variability analysis, using different techniques both in time and frequency domain. Proposed parameters have shown some limitations, due to their inability to analyze nonlinear dynamics, involved in heart rate control and relevant for clinical aims. In the last decades, nonlinear analysis methods have gained a growing interest. Here, we described an application of a nonlinear analysis (symbolic dynamic analysis) and introduced a new index to quantify foetal heart rate variability, in a simple and concise way, in healthy foetuses near to term. The index was able to highlight differences in foetal heart rate variability, not always so evident on printed cardiotocographic signals, and resulted significantly correlated with the different kinds of delivery (spontaneous or caesarean); in particular, higher variability index values corresponded to spontaneous delivery.