Poincare analysis of fetal heart rate pattern: effect of observation period

The purpose of this study was to determine to what degree the chaotic structure in fetal heart rate variability is maintained for varying observation periods. We investigated this by evaluating the dispersion characteristics in Poincare plots on 3-, 5-, 10-, 15-, 20-, and 30-minute segments of R-R intervals for a fetus in active sleep. Our results showed that chaotic structure and dispersion patterns were present across all observation periods as compared to the randomized samples, where the dispersion pattern was consistently high and there was no structure. We conclude that the fetal heart rate pattern is chaotic and this chaotic structure is maintained in intervals as short as 3-5 minutes. The variability in the dispersion pattern is increased at these shorter observation periods.