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The article presents guidelines on the determination and treatment of intrapartum fetal heart rate (FHR) patterns. The authors adopted a five-tier system to classify the FHR patterns and modified the color-coded classification. They propose a standardized management protocol according to FHR pattern, level for both doctors and midwives.

Background: Detrended fluctuation analysis (DFA) has recently been validated as an excellent method by which to analyze heart rate variability and distinguish healthy subjects from patients with various types of the cardiac nervous system dysfunction. Methods: One hundred and nineteen fetal heart rate (FHR) recordings obtained from healthy normal fetuses and 68 recordings obtained from small-for-gestational-age (SGA) fetuses were analyzed by DFA to examine gestational and pathologic changes of the scaling exponent, α. Results: In normal fetuses, a significant increase was observed in both the short-term (≤30 s) α1 and long-term (>30 s) α2 scaling exponents according to gestational age. The α1 values of SGA fetuses were not significantly different from those of healthy normal fetuses; however, the α2 values of the former group (0.955 ± 0.152) were significantly higher than those of normal subjects (0.887 ± 0.128; p = 0.001). Conclusion: The α2 exponent appears to be a sensitive probe for detecting subtle, and possibly important, changes that occur in fetuses with intrauterine growth restriction, and may be helpful in the early and noninvasive detection of placental insufficiency or incipient intrauterine growth restriction. The use of DFA techniques offers great promise for understanding FHR behavior. Copyright © 2007 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Background: Decelerations of fetal heart rate (FHR) are the results of many pathophysiological factors that modulate the intrinsic rate of the heart. FHR change is a complex phenomenon and can be viewed as a type of nonlinear dynamic system. This paper presents a qualitative model of FHR decelerations based on catastrophe theory, especially to account for abrupt heart rate changes seen in variable decelerations. Methods: One of the elementary catastrophes, the cusp catastrophe, was used to model FHR changes seen in variable, late, and early decelerations. Results: Catastrophe theory describes typical variable decelerations as an abrupt response to a slowly changing force of attack (uterine contraction) and physiological defense. Because of its three-dimensionality and topological features, the cusp catastrophe model provides a qualitatively satisfying description of FHR decelerations. Conclusion: The organized complexity of living systems offers the best hope for the application of catastrophe theory. The nature of the elementary catastrophes will be essential knowledge in the mathematical analysis of biology. Copyright © 2006 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Abstract: Background: Many studies on the physiology of the cardiovascular system reported that nonlinear chaotic dynamics may govern the generation of the heart rate signal. Objective: To examine whether the heart rate dynamics of an intrauterine growth restricted (IUGR) fetus is different from a healthy normal fetus by nonlinear methods of time series analysis. Design of the study: One hundred nineteen fetal heart rate (FHR) recordings from healthy normal fetuses, and 69 recordings from IUGR fetuses were analyzed. Nonlinear analyses included attractor reconstruction, calculation of the largest Lyapunov exponents using the Wolf algorithm, and estimation of correlation dimension. The largest Lyapunov exponents from normal fetuses were checked by means of surrogate-data test. Results: Abnormal FHR patterns of IUGR fetuses such as decreased variability and repetitive late decelerations presented a remarkably different structure in the reconstructed attractor. Surrogate data suggest that the FHR of healthy normal fetuses has unique nonlinear characteristics. The largest Lyapunov exponents were positive for all of 119 healthy normal fetuses, indicating that the FHR control system is sensitive to initial conditions. The values of IUGR fetuses were significantly lower than those of normal subjects. In normal fetuses, significant changes of correlation dimension according to gestational age were observed. In IUGR fetuses, however, such changes were not found. Conclusions: The heart rate dynamics of IUGR fetuses is less chaotic than that of normal fetuses. Decreased system complexity suggested by correlation dimension may limit the IUGR fetuses'' ability to maintain cardiovascular integrity, and therefore, to adapt to the variety of internal and external cardiovascular stresses. [Copyright &y& Elsevier]

Abstract: Objective: Our objective was to examine whether heart rate time series of healthy normal fetuses possess fractal properties and, if so, to determine whether consistent changes in fractal features according to gestational age exist. Design of the study: One hundred nineteen fetal heart rate (FHR) recordings in 55 singleton pregnancies between the 22nd and 41st weeks were analyzed. Fractal analysis developed by Higuchi was performed. Changes of fractal dimension were examined according to gestational age. Results: Two characteristic scaling regions were present in each FHR trace. The fractal dimension defined within 500 ms to 5 s (D S; median 1.396, range 1.273–1.642) was lower than that defined longer than 30 s (D L; median 1.933, range 1.492–2.049) in every case. These two values were significantly different (p <0.001). There was a statistically significant difference in the values of D S between (22–29 weeks, mean 1.323), (30–33 weeks, mean 1.443) (p =0.004), (34–35 weeks, mean 1.418) (p =0.002), (36 weeks, mean 1.409) (p =0.030), (37–38 weeks, mean 1.394) (p =0.006), and (40–41 weeks, mean 1.452) (p =0.001), respectively. D S values between (40–41 weeks), (37–38 weeks) (p =0.012), and (39 weeks, mean 1.369) (p =0.030), respectively, were also significantly different. The values of D L decreased from 22–39 weeks (median 1.941) to 40–41 weeks (median 1.891) (p =0.008). Conclusions: Two distinct fractal structures within the FHR variation were identified. Fractal features of heart rate of healthy normal fetuses change significantly during pregnancy period. Fractal analysis may be useful for evaluating FHR variation. [Copyright &y& Elsevier]