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. 2023 Jan 13:13:1056679.
doi: 10.3389/fendo.2022.1056679. eCollection 2022.

Uterine activity modifies the response of the fetal autonomic nervous system at preterm active labor

Rocio Lizbeth Olmos-Ramírez  1 , Miguel Ángel Peña-Castillo  1 , Hugo Mendieta-Zerón  2   3 , José Javier Reyes-Lagos  3
Affiliations

Uterine activity modifies the response of the fetal autonomic nervous system at preterm active labor

Rocio Lizbeth Olmos-Ramírez et al. Front Endocrinol (Lausanne). .

Abstract

Background: The autonomic nervous system of preterm fetuses has a different level of maturity than term fetuses. Thus, their autonomic response to transient hypoxemia caused by uterine contractions in labor may differ. This study aims to compare the behavior of the fetal autonomic response to uterine contractions between preterm and term active labor using a novel time-frequency analysis of fetal heart rate variability (FHRV).

Methods: We performed a case-control study using fetal R-R and uterine activity time series obtained by abdominal electrical recordings from 18 women in active preterm labor (32-36 weeks of gestation) and 19 in active term labor (39-40 weeks of gestation). We analyzed 20 minutes of the fetal R-R time series by applying a Continuous Wavelet Transform (CWT) to obtain frequency (HF, 0.2-1 Hz; LF, 0.05-0.2 Hz) and time-frequency (Flux0, Flux90, and Flux45) domain features. Time domain FHRV features (SDNN, RMSSD, meanNN) were also calculated. In addition, ultra-short FHRV analysis was performed by segmenting the fetal R-R time series according to episodes of the uterine contraction and quiescent periods.

Results: No significant differences between preterm and term labor were found for FHRV features when calculated over 20 minutes. However, we found significant differences when segmenting between uterine contraction and quiescent periods. In the preterm group, the LF, Flux0, and Flux45 were higher during the average contraction episode compared with the average quiescent period (p<0.01), while in term fetuses, vagally mediated FHRV features (HF and RMSSD) were higher during the average contraction episode (p<0.05). The meanNN was lower during the strongest contraction in preterm fetuses compared to their consecutive quiescent period (p=0.008).

Conclusion: The average autonomic response to contractions in preterm fetuses shows sympathetic predominance, while term fetuses respond through parasympathetic activity. Comparison between groups during the strongest contraction showed a diminished fetal autonomic response in the preterm group. Thus, separating contraction and quiescent periods during labor allows for identifying differences in the autonomic nervous system cardiac regulation between preterm and term fetuses.

Keywords: autonomic function; continuous wavelet transform (CWT); fetal heart rate variability; preterm labor; uterine contractions.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Figure 1
Figure 1
Window segmentation of 50 seconds for the fetal R-R signal and time-frequency representation. Pointed area: contraction period, striped area: quiescent interval. The upper panel shows the fetal beat-to-beat R-R time series; the middle panel shows the time-frequency representation of the fetal R-R time series; the lower panel shows the TOCO-like signal.
Figure 2
Figure 2
Window segmentation of 50 seconds on the representative frequency bands time series. Pointed area: contraction interval of study. Striped area: quiescent interval of study. Panel (A) shows the frequency band delimitation on the time-frequency representation of the R-R time series. Panel (B) shows contraction and quiescent analysis window delimitation over the frequency bands time series (upper and middle subplots) aligned with the TOCO-like signal (lower subplot).
See this image and copyright information in PMC

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