Basic Sciences and Engineering Division, Metropolitan Autonomous University (UAM) Campus Iztapalapa, Mexico City, Mexico.
Health Institute of the State of Mexico (ISEM), "Mónica Pretelini Sáenz" Maternal-Perinatal Hospital, Toluca, Mexico.
Front Endocrinol (Lausanne). 2023 Jan 13;13:1056679. doi: 10.3389/fendo.2022.1056679. eCollection 2022.
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).
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.
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).
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.
早产儿的自主神经系统成熟度与足月儿不同。因此，他们对分娩时子宫收缩引起的短暂性缺氧的自主反应可能不同。本研究旨在使用胎儿心率变异性（FHRV）的新时频分析方法比较早产儿和足月儿主动分娩时子宫收缩胎儿自主反应的行为。
我们对 18 名处于活跃早产（32-36 周）和 19 名活跃足月（39-40 周）产妇的腹部电记录获得的胎儿 R-R 和子宫活动时间序列进行病例对照研究。我们通过连续小波变换（CWT）对胎儿 R-R 时间序列进行了 20 分钟的分析，以获得频域（HF，0.2-1 Hz；LF，0.05-0.2 Hz）和时频域（Flux0、Flux90 和 Flux45）特征。还计算了时域 FHRV 特征（SDNN、RMSSD、meanNN）。此外，通过根据子宫收缩和静止期片段对胎儿 R-R 时间序列进行超短 FHRV 分析。
当在 20 分钟内计算 FHRV 特征时，早产和足月分娩之间没有发现显著差异。然而，当在子宫收缩和静止期之间进行分段时，我们发现了显著差异。在早产组中，平均收缩期与平均静止期相比，LF、Flux0 和 Flux45 更高（p<0.01），而在足月胎儿中，迷走神经介导的 FHRV 特征（HF 和 RMSSD）在平均收缩期更高（p<0.05）。与连续静止期相比，早产儿在最强收缩期的平均 NN 较低（p=0.008）。
早产儿平均对宫缩的自主反应表现为交感神经优势，而足月儿则通过副交感神经活动作出反应。与最强收缩期的组间比较显示，早产儿组的胎儿自主反应减弱。因此，在分娩期间分离收缩期和静止期可以识别早产儿和足月儿之间自主神经系统心脏调节的差异。
