Detrended Fluctuation Analysis of Heart Rate Variability in Normal and Growth-Restricted Fetuses

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, alpha. RESULTS: In normal fetuses, a significant increase was observed in both the short-term (<or=30 s) alpha(1) and long-term (>30 s) alpha(2) scaling exponents according to gestational age. The alpha(1) values of SGA fetuses were not significantly different from those of healthy normal fetuses; however, the alpha(2) 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 alpha(2) 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.