A Unified Contraction Characterization for the Identification of Spontaneous Onset of Labor in Term Nulliparous Women via Multi-Channel Electrohysterography and Tocodynamometer
Authors: XU Jinshan , Shen Junhua , Lin Yiwei , Bai Xiaoxia , Pumir Alain , Li Baohua 
Published: September 2024

Abstract

Background
Strong and synchronized contractions that occur in the last stage of pregnancy are essential for onset of labor. In clinics, the lack of effective description of these characteristics results in inaccurate prediction of the onset of labor. The commonly used contraction monitoring device tocodynamometer (TOCO) detects contractions with relatively high specificity but is unable to quantify the strength and synchrony. The electrohysterography (EHG) quantifies the myoelectric activities that trigger contractions of muscle cells under the electrodes. Therefore, multiple channel EHG signals are well suited for characterizing the strength and synchrony of uterine contractions via their spatiotemporal pattern.
Object:
The purpose of this study was to provide quantitative descriptions of the contraction characteristics and to investigate their significance for predicting the spontaneous onset of labor in nulliparous women.
Study Design:
100 pregnant women with a gestational age of more than 37 weeks were recruited for the study. Multichannel EHG and tocodynamometer recordings were performed simultaneously for 46 of them, both during pregnancy and during labor (defined a time to onset of labor (TTL) less than 24 h). Contractions were identified from the TOCO recordings, and then the frequency and duration of contractions were determined. The multichannel EHG segments under the identified contractile time windows were used to calculate the strength and level of synchrony. Statistical analyses were carried to demonstrate the difference of these variables between the pregnant and labor groups. Multivariate logistic regression was created to provide obstetricians with an assessment tool in predicting spontaneous onset of term labor.
Results
The frequency, duration, strength, and level of synchrony of uterine contractions for 46 pregnant women during their 37 weeks of gestation to the onset of labor were quantified. All constructed features in labor, with the exception of concordance correlation-based synchrony \(\:\psi\:\), showed statistically significant differences from those in pregnant phase, with degree of synchrony described by the sample entropy SamEn being the strongest feature for distinguishing pregnant and labor (0.5154 ± 0.1720 vs. 0.3555 ± 0.1422, \(\:p=0.00001\)). The multivariate logistic regression model constructed from these features showed high significance in identifying the onset of spontaneous labor in nulliparous women, with an AUC value of 0.80.
Conclusion
The contraction properties in terms of frequency, duration, strength, and level of synchrony have been quantitated. Continuous observations on 46 pregnant women throughout their pregnancy demonstrated statistically significant difference between contractions in pregnant and labor phase, which enabled a prediction model on spontaneous onset of labor in term nulliparous women.