Assessment of maternal heart-rate variability during labor using wavelet-based power spectral analysis.

Objective: Changes in the maternal cardiac autonomic nervous system were assessed in the presence and absence of uterine contractions by analyzing maternal heart-rate variability during labor using wavelet-based power spectral analysis.

Methods: We assessed the heart-rate variability in 20 pregnant women during labor and in 15 pregnant women with threatened premature labor with the use of wavelet-based power spectral analysis.

Results: There was no significant difference in high-frequency components between the uterine contraction and non-contraction periods. The intensities of the low-frequency and very-low-frequency components during uterine contractions were significantly stronger than the corresponding intensities between uterine contractions.

Conclusion: Maternal sympathetic activity was upregulated during uterine contractions, and influenced the very-low-frequency components. This method of analysis may represent a novel means of identifying uterine contractions.