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

Abstract

BackgroundThe 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).MethodsWe 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.ResultsNo 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).ConclusionThe 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.

Automated Method for Uterine Contraction Extraction and Classification of Term Versus Pre-Term EHG Signals

“…Labor, the physiological procedure through which a fetus is expelled from the uterus, is characterized by regular uterine contractions, cervical effacement, and dilation. The World Health Organization (WHO) defines preterm birth as labor starting earlier than expected and the baby being born before 37 weeks of pregnancy has passed 37-42 weeks as a term, and over 42 weeks as post-term [2]. Experiencing complications during pregnancy can lead to premature birth which consistently increases the risk of the physical condition of very preterm children and parental mental health problems [3] [4].…”

“…In the TOCO method, a pressure transducer was placed on the patient's abdomen and contractions were measured. The intrauterine pressure significantly changes as a result of the uterine contractions [2]. It detects pressure force produced by the contorting abdomen and converts this mechanical energy to an electrical signal.…”