A Comprehensive Study of Uterine Muscle Activity During the Third Trimester: Comparison of Singleton and Multiple Gestations

Abstract

Objective: Electrohysterography (EHG) has been shown to provide valuable information for assessing preterm birth risk. However, few studies have focused on multiple gestations (MG), a well-known risk factor for preterm birth. This study aimed to comprehensively characterize and compare uterine EHG signals between singleton (SG) and MG pregnancies during the third trimester. Method: This prospective cohort study analyzed 383 EHG recordings from 61 SG and 92 MG women during the third trimester. A whole-window approach was used to extract four key EHG features: peak-to-peak amplitude (PPA), Kurtosis of the Hilbert Envelope (KHE), median frequency (MDF) and sample entropy (SampEn). Generalized additive models (GAM) were applied to evaluate temporal trends across gestational age (GA) and gestation type (SG and MG). Results: In SG pregnancies, PPA and KHE progressively increased, with a significant rise in KHE at labour. MDF remained stable until labour, while SampEn gradually declined, especially at term. MG pregnancies showed similar but less pronounced trends: MG exhibited a notably earlier activation of uterine activity than SG before 32 weeks of gestation (WoG), and a slowing-down electrophysiological progression beyond 32 WoG, resulting in similar characteristics with no significant differences. Conclusion: These findings provide electrophysiological evidence suggesting that MG pregnancies may enter a labour-preparatory state earlier, potentially increasing the PTB risk, while the later convergence of EHG features may indicate compensatory mechanisms to delay labour. This work integrates EHG signal analysis with clinical obstetric care, offering valuable insights for clinical management and early PTB risk assessment in MG pregnancies.