On the management of maternal pushing during the second stage of labor: a biomechanical study considering passive tissue fatigue damage accumulation - 20/07/22
Abstract |
Background |
During the second stage of labor, the maternal pelvic floor muscles undergo repetitive stretch loading as uterine contractions and strenuous maternal pushes combined to expel the fetus, and it is not uncommon that these muscles sustain a partial or complete rupture. It has recently been demonstrated that soft tissues, including the anterior cruciate ligament and connective tissue in sheep pelvic floor muscle, can accumulate damage under repetitive physiological (submaximal) loads. It is well known to material scientists that this damage accumulation can not only decrease tissue resistance to stretch but also result in a partial or complete structural failure. Thus, we wondered whether certain maternal pushing patterns (in terms of frequency and duration of each push) could increase the risk of excessive damage accumulation in the pelvic floor tissue, thereby inadvertently contributing to the development of pelvic floor muscle injury.
Objective |
This study aimed to determine which labor management practices (spontaneous vs directed pushing) are less prone to accumulate damage in the pelvic floor muscles during the second stage of labor and find the optimum approach in terms of minimizing the risk of pelvic floor muscle injury.
Study Design |
We developed a biomechanical model for the expulsive phase of the second stage of labor that includes the ability to measure the damage accumulation because of repetitive physiological submaximal loads. We performed 4 simulations of the second stage of labor, reflecting a directed pushing technique and 3 alternatives for spontaneous pushing.
Results |
The finite element model predicted that the origin of the pubovisceral muscle accumulates the most damage and so it is the most likely place for a tear to develop. This result was independent of the pushing pattern. Performing 3 maternal pushes per contraction, with each push lasting 5 seconds, caused less damage and seemed the best approach. The directed pushing technique (3 pushes per contraction, with each push lasting 10 seconds) did not reduce the duration of the second stage of labor and caused higher damage accumulation.
Conclusion |
The frequency and duration of the maternal pushes influenced the damage accumulation in the passive tissues of the pelvic floor muscles, indicating that it can influence the prevalence of pelvic floor muscle injuries. Our results suggested that the maternal pushes should not last longer than 5 seconds and that the duration of active pushing is a better measurement than the total duration of the second stage of labor. Hopefully, this research will help to shed new light on the best practices needed to improve the experience of labor for women.
Le texte complet de cet article est disponible en PDF.Key words : finite element method, low-cycle fatigue failure, management of labor, maternal pushes, pelvic floor muscle, second stage of labor, vaginal delivery
Plan
J.A.A.M.’s institution received a US National Institutes of Health grant (grant number R44 HD 096987) for him and a student to analyze the Materna LLC Prep device data on the relationship between birth canal dilation force and displacement during the first stage of labor. That research did not address any topics found in the current paper. The remaining authors report no conflict of interest. |
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The authors acknowledge the support from the Portuguese Foundation of Science under grant number SFRH/BD/136213/2018 and under the research project UIDB/50022/2020. The funding sources were not involved in preparing the manuscript and conducting the research. |
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Cite this article as: Vila Pouca MCP, Ferreira JPS, Parente MPL, et al. On the management of maternal pushing during the second stage of labor: a biomechanical study considering passive tissue fatigue damage accumulation. Am J Obstet Gynecol 2022;227:267.e1-20. |
Vol 227 - N° 2
P. 267.e1-267.e20 - août 2022 Retour au numéroBienvenue sur EM-consulte, la référence des professionnels de santé.
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