The effect of gender, gestational age and behavioral states on fetal heart rate variability

Cardiotocography (CTG) is the most frequently used electronic fetal monitoring technique, both in the antepartum and intrapartum periods. A few systems for computer analysis of CTG tracings have been developed, but there is still a large room for improvement in their capacity to diagnose fetal hypoxia/acidosis. Research on fetal heart rate (FHR) analysis has shown that several factors are not commonly considered in such systems, and these can significantly influence the computation of FHR indices: among them are gender, gestational age and fetal behavioral states. A short review is provided on the influence of these factors in FHR analysis, particularly in linear (time- and frequency-domain) and nonlinear (entropy) indices. In conclusion, the effect of gender, gestational age and behavioral states on FHR analysis may need to be considered for the improvement of computer systems developed for that purpose.