Linear and non-linear analysis of uterine contraction signals obtained with tocodynamometry in prediction of operative vaginal delivery

Hernâni Gonçalves; Mariana Morais; Paula Pinto; Diogo Ayres-de-Campos; João Bernardes

doi:10.1515/jpm-2016-0036

Article

Linear and non-linear analysis of uterine contraction signals obtained with tocodynamometry in prediction of operative vaginal delivery

Hernâni Gonçalves , Mariana Morais , Paula Pinto , Diogo Ayres-de-Campos and João Bernardes

Published/Copyright: August 26, 2016

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From the journal Journal of Perinatal Medicine Volume 45 Issue 3

Abstract

Objective:

The aim of this study was to explore whether linear and non-linear analysis of uterine contraction (UC) signals obtained with external tocodynamometry can predict operative vaginal delivery (OVD).

Materials and methods:

The last 2 h before delivery (H₁ and H₂) of 55 UC recordings acquired with external tocodynamometry in the labour ward of a tertiary care hospital were analysed. Signal processing involved the quantification of UCs/segment (UC_N), and the linear and non-linear indices: Sample Entropy (SampEn) measuring signal irregularity; interval index (II) measuring signal variability, both of which may be associated with uterine muscle fatigue, and high frequency (HF), associated with maternal breathing movements. Thirty-two women had normal deliveries and 23 OVDs. Statistical inference was performed using 95% confidence intervals (95% CIs) for the median, and areas under the receiver operating curves (auROCs), with univariate and bivariate analyses.

Results:

A significant association was found between maternal body mass index (BMI) and UC signal quality in H₁, with moderate/poor signal quality being more frequent with higher maternal BMI. There was an overall increase in contraction frequency (UC_N), signal regularity (SampEn), signal variability (II), and maternal breathing (HF) from H₁ to H₂. The OVD group exhibited significantly higher values of signal irregularity and variability (SampEn and II) in H₁, and higher contraction frequency (UC_N) and maternal breathing (HF) in H₂. Modest auROCs were obtained with these indices in the discrimination between normal and OVDs.

Conclusions:

The results of this exploratory study suggest that analysis of UC signals obtained with tocodynamometry, using linear and non-linear indices associated with muscle fatigue and maternal breathing, identifies significant changes occurring during labour, and differences between normal and OVDs, but their discriminative capacity between the two types of delivery is modest. Further refinement of this analysis is needed before it may be clinically useful.

Keywords: Cardiotocography; digital signal processing; entropy; operative vaginal delivery (OVD); spectral analysis

Acknowledgement

Hernâni Gonçalves is financed by a post-doctoral grant (SFRH/BPD/69671/2010) from the Fundação para a Ciência e a Tecnologia (FCT), Portugal.

Conflict of interest statement: Diogo Ayres-de-Campos and João Bernardes have been involved in the development of the Omniview-SisPorto® system for FHR analysis (Speculum, Portugal). Royalties are fully converted to institutional research funds.

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The authors stated that there are no conflicts of interest regarding the publication of this article.

Received: 2016-1-29

Accepted: 2016-7-25

Published Online: 2016-8-26

Published in Print: 2017-4-1

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Articles in the same Issue

https://doi.org/10.1515/jpm-2016-0036

Keywords for this article

Cardiotocography; digital signal processing; entropy; operative vaginal delivery (OVD); spectral analysis