Biomechanical Analyses of the Efficacy of Patterns of Maternal Effort on Second-Stage Progress

Abstract

OBJECTIVE-To develop and use a biomechanical computer model to simulate the effect of varying the timing of voluntary maternal pushes during uterine contraction on second-stage labor duration.METHODS-Published initial pelvic floor geometry was imported into technical computing software to build a simplified 3-D biomechanical model with six representative viscoelastic levator muscle bands interconnected by a hyperelastic iliococcygeal raphé. An incompressible sphere simulated the molded fetal head. Forces from uterine contraction and voluntary expulsive efforts were summed to push the model fetal head along the Curve of Carus opposed by the resistance of the pelvic floor structures to stretch. Holding uterine maximal contraction force and push strength constant, pushes were timed before ("Pre"), at ("Peak"), and after ("Post") maximal uterine contraction force. The effect of different combinations of pushes on second stage duration and the number of pushes required for delivery were evaluated.RESULTS-Calculated second stage durations ranged from 57.5 minutes ("triple" or Pre-PeakPost pattern) to 75.8 minutes ("pre-push" and "post-push" patterns). Delivery with the "triple push" pattern required 59 voluntary pushes, while the "peak push" pattern required 23 voluntary pushes, a 61% reduction. The corresponding reduction for the "pre-and-peak push" pattern was 29%, the "peak-and-post push" pattern was 30%, the "pre-push" pattern was 54%, and the "postpush" pattern was 56%.CONCLUSION-Although the "triple push" pattern resulted in a 16% shorter second stage, this came at the energetic expense of a 61% increase in the number of pushes required.

The determinants of minimal levator hiatus and their relationship to the puborectalis muscle and the levator plate

“…Lateral to these fibres are a variable number of puborectalis fibres. Therefore, levator ani injury sustained during childbirth at this location would most certainly involve the pubococcygeus, as shown by the 3D modelling performed by Lien and colleagues, and the cephalad edge of the puborectalis attachment, if the injury extends beyond the puboanalis fibres. Total unilateral or bilateral disruption of all the muscles involved in the anterior attachment of the MLH would constitute what has been called levator avulsion in the literature.…”

“…The MLH has been used as a marker for levator trauma, but because of major variations in terminology and understanding of the levator anatomy, there is much confusion about which muscles form the borders of the MLH. Knowing exactly which muscles contribute to the formation of the MLH is important because it has been shown that this is the area most prone to injury during childbirth …”

“…Knowing exactly which muscles contribute to the formation of the MLH is important because it has been shown that this is the area most prone to injury during childbirth. 10,11 The objective of the current study was to define the muscular borders of MLH by using cadaveric dissection and 3D endovaginal ultrasound (3D EVUS) in normal nulliparous women by measuring MLH area, puborectalis hiatus (PRH) area, anorectal angle (ARA), and a novel measurement called levator plate descent angle (LPDA).…”

Ultrasongraphic age‐related changes of the pelvic floor muscles in nulliparous women and their association with pelvic floor symptoms: A pilot study

“…1 Aging is also a strong risk factors for pelvic floor prolapse, and urinary incontinence. [2][3][4][5][6][7][8] In designing a study investigating the effect of aging it is important to remove vaginal birth as a confounding factor. A previous study of Quiroz et al had shown that age does not affect visualization of the levator ani in nulliparous women using 3D ultrasound.…”

Levator plate descent correlates with levator ani muscle deficiency

“…The total levator ani volume by MRI reconstruction has been shown to be 46.6 ± 5.9 ml . The levator ani muscle based on muscle fiber counts and volume can be divided into three groups: (1) iliococcygeus/pubococcygeus, that is, pubovisceralis (PVM), (2) puborectalis (PR), and (3) puboanalis/puboperinealis (PA) . Based on their function, PVM is the elevator, PR is the squeezer, and PA is the stabilizer, these muscles intertwine with each other and give lateral support to the levator plate which is connected with anococcygeal ligament posteriorly.…”