Application of Symbolic Dynamics in Fetus to Study Placental Insufficiency and Metabolic Acidosis

Objective: To assess the possibility to diagnose placental insufficiency and metabolic acidosis by analysing the fetal heart rate (FHR) variability by using non-linear methods; symbolic dynamics or traditional linear stochastic theory. Study design The recorded FHR signal sets from the last hour of delivery in 21 live born fetuses were analysed. The complexity of the FHR variability was described by an entropy parameter using symbolic dynamics as well as by standard deviation of each FHR. Cases with placental insufficiency and metabolic acidosis were identified from cord artery blood gas analyses. Results No significant correlation was found between the entropy parameter and the arterial pH or between the standard deviation and the arterial pH. Results are improving when combining the two (entropy parameter and standard deviation) in a multiple regression analysis. Only one of the analysed cases was identified with metabolic acidosis (cord artery pH < 7,0 and Base Deficit > 12,0 mmol/L). Conclusion To know if it is possible to diagnose placental insufficiency and metabolic acidosis by analysing the FHR variability by using non-linear methods, symbolic dynamics or traditional linear stochastic theory, a study with FHR not influenced by uterine contractions during labour is needed to conclude if the lack of correlation is caused by uterine contractions or insufficient mathematical methodology