Premature birth and its associated complications are one of the biggest global health problems, since there is currently no effective screening method in clinical practice to accurately identify the true Preterm Birth (PTB) from the false threatened ones. Despite the high prevalence of PTB in multiple gestation (MG) women which amounted up to 60%, in the literature there is any work about their uterine myoelectric activities in vivo system. Electrohysterography (EHG) has been emerged as an alternative technique for predicting PTB in single gestation (SG) women.

The aim of this study was to characterize and compare the uterine myoelectrical activity in vivo system of SG and MG women in regular check-ups, to provide the basis for early detection and prevention of preterm labour in MG.

A prospective observational cohort study was conducted on 31 SG and 18 MG women between the 28^th and 32^th WoG who underwent regular check-ups in the Polytechnic and University Hospital La Fe (Valencia, Spain). The 30-minute bipolar recording was filtered in the 0.1-4 Hz bandwidth and downsampled to 20 Hz. Signal analysis was performed in 120-second moving windows with 50% overlap, after removing artefacts by a double- blind expert process. A set of 8 temporal, spectral and non-linear parameters were calculated: root mean square (RMS), kurtosis of the Hilbert envelope (KHE), median frequency (MDF), H/L ratio, and sample entropy (SampEn) and bubble entropy (BubbEn) calculated in the whole bandwidth (WBW) and the fast wave high (FWH). The 10th, 50th and 90th percentiles of all windows analysed were calculated to obtain representative values of the recordings. For each parameter and percentile, statistically significant differences between the SG and MG groups and their statistical power (SP) were analysed to determine both the existence of an effect and substantive significance, respectively.

In comparison to SG, MG EHG exhibited significant higher impulsiveness and higher predictability than SG which was reflected in the KHE (SP₁₀ = 85.2, p₁₀ < 0.001) and entropy measures (SampEn FWH: SP₅₀ = 62.0, p₅₀ = 0.0.016; SP₉₀ = 52.5, p₉₀ = 0.059. BubbEn FWH: SP₅₀ = 75.2, p₅₀ < 0.001; SP₉₀ = 60.3, p₉₀ = 0.002), suggesting an accelerated evolution of uterine electrophysiological condition. In addition, several EHG parameters were found to significantly correlate with foetal weight such as amplitude (RMS: r₉₀ = 0.311, p₉₀ = 0.006), signal impulsiveness (KHE: r₁₀ = 0.311, p₁₀ = 0.006) and entropy measures (SampEn FWH: r₅₀ = −0.317, p₅₀ = 0.005*; r₉₀ = −0.279, p₉₀ = 0.013*. BubbEn FWH: r₅₀ = −0.370, p₅₀ = 0.001*; r₉₀ = −0.313, p₉₀ = 0.005*), suggesting an electromechanical coupling between uterine overdistension and contractile activity in vivo system.

In comparison to SG women, MG showed higher impulsiveness and predictability in early third gestational trimester, as reflected in KHE, SampEn and BubbEn, respectively. We found similar cell excitability between SG and MG women far from delivery. In addition, we confirmed the relationship between uterine overdistension and surface myoelectric activity, revealing the electromechanical coupling pathway in uterine smooth muscle. Therefore, contextualized EHG-biomarkers would provide valuable information for early detection of PTB risk, which would allow clinicians better PTB management through personalised therapeutic interventions.