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Fetal autonomic responses inferred from heart rate variability during recurrent decelerations without acidosis-An
Shoichi Magawa1, Masafumi Nii1, Yuya Tamaishi1
1Department of Obstetrics and Gynecology, Mie University Graduate School of Medicine, Tsu, Japan.
Objective:
Recurrent fetal heart rate (FHR) decelerations without acidosis are frequently observed during labor; however, the underlying autonomic mechanisms remain incompletely understood. This study explored fetal autonomic responses to recurrent decelerations using FHR and FHR variability (FHRV) parameters.
Methods:
This retrospective observational study included healthy women with singleton pregnancies, no pregnancy complications requiring treatment, and an umbilical artery pH >7.2 at delivery. Continuous FHR monitoring using fetal head electrodes was performed for ≥2 h before delivery (June-December 2021). FHRV was assessed using time-domain, frequency-domain, and nonlinear indices.
Results:
Twenty-four patients were included. Baseline FHR did not differ between groups. In the recurrent deceleration group, root mean square of successive differences and high-frequency power were higher during the final 60 min before delivery. No differences were observed in standard deviation of normal-to-normal intervals or very-low-frequency power. Sample entropy was also higher, suggesting increased complexity of autonomic regulation.
Conclusion:
Fetuses with recurrent decelerations without acidosis demonstrated patterns consistent with increased vagal modulation, as inferred from FHRV indices. These findings may reflect an adaptive autonomic response; however, given the exploratory nature and small sample size, further studies are warranted.
