Differences between external and internal fetal heart rate monitoring during the second stage of labor: a prospective observational study

Inês Nunes; Diogo Ayres-de-Campos; Cristina Costa-Santos; João Bernardes

doi:10.1515/jpm-2013-0281

Article

Differences between external and internal fetal heart rate monitoring during the second stage of labor: a prospective observational study

Inês Nunes , Diogo Ayres-de-Campos , Cristina Costa-Santos and João Bernardes

Published/Copyright: January 16, 2014

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From the journal Journal of Perinatal Medicine Volume 42 Issue 4

Abstract

Objective: To compare fetal heart rate (FHR) signals acquired simultaneously by an external ultrasound probe and a scalp electrode during the second stage of labor.

Methods: This was a prospective observational study in a labor ward of a tertiary care university hospital. The population was women in labor with uneventful singleton pregnancies at term. Simultaneous external and internal FHR monitoring was performed in 67 consecutively recruited women during the second stage of labor. Cases were subsequently excluded if the trace length was under 40 min, cesarean birth occurred, or the interval between trace-end and birth exceeded 5 min, leaving a total of 33 traces for analysis. The last 40–60 min of these traces were analyzed by a computer system (Omniview-SisPorto^® 3.5; Speculum^®, Lisbon, Portugal) to quantify cardiotocographic parameters. Paired sample t-test and Bland-Altman limits of agreement (LoA) were used for statistical analysis, setting significance at 0.05. The main outcome measures were signal loss, FHR baseline, periodic events, and percentage of periodic events coinciding with contractions.

Results: A higher signal loss was observed with external monitoring [10% vs. 4%; P<0.001, LoA=(–6, 18)]. No differences were found in mean FHR baseline [129 bpm vs. 130 bpm, P=0.245, LoA=(–15, 12)], but more accelerations [12 vs. 8, P<0.001, LoA=(–5, 13)] and less decelerations [8 vs. 10, P<0.001, LoA=(–8, 4)] were detected with external monitoring. With this method there were also more accelerations (66% vs. 55%, P=0.036) and less decelerations (68% vs. 81%, P=0.017) coinciding with contractions.

Conclusions: External FHR monitoring during the second stage of labor results in higher signal loss, increased number of accelerations, and decreased number of decelerations when compared with internal monitoring.

Keywords: Cardiotocography; heart rate, fetal; labor, second stage; signal processing, computer-assisted

Corresponding author: Dr. Inês Nunes, Institute of Biomedical Engineering, Department of Obstetrics and Gynecology, School of Medicine, University of Porto, Alameda Hernâni Monteiro, 4200-319 Porto, Portugal, Tel.: +351 916557429, Fax: +351 225513600, E-mail: nunes.ing@gmail.com

Acknowledgments

The authors would like to thank the midwives involved in the recruitment and acquisition of the traces and Paulo Sousa, for converting the traces to an analyzable format.

References

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

Received: 2013-10-17

Accepted: 2013-11-25

Published Online: 2014-1-16

Published in Print: 2014-7-1

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Articles in the same Issue

https://doi.org/10.1515/jpm-2013-0281

Keywords for this article

Cardiotocography; heart rate, fetal; labor, second stage; signal processing, computer-assisted