Assessment of the bearing‐down manoeuvre in pregnancy and detection of paradoxical levator ani muscle contraction using 2D transperineal ultrasound and vaginal palpation: a concurrent validity and inter‐rater reliability study

To examine the concurrent validity and inter‐rater reliability of vaginal palpation as a measure of the quality of the bearing‐down manoeuvre (BDM) and the detection of a paradoxical levator ani muscle contraction (LAM) in pregnant women, compared with 2D transperineal ultrasound (TPUS).


| I N TRODUC TION
2][3][4] During the BDM, the levator ani muscle (LAM) should lengthen and descend. 2 A poor BDM is associated with a shortening of the LAM, often described as a paradoxical contraction.6][7] Anal manometry has been established as the gold standard assessment tool in screening for paradoxical LAM movement in people with chronic constipation. 3However, the assessment of the BDM in pregnancy has been less researched.6][7] In the clinical setting a real-time ultrasound, or a clinician skilled to use it, is not always accessible.Vaginal palpation is a clinically accessible and meaningful method of assessing the LAM and its response to a rise in IAP, such as the BDM.
The presence of a paradoxical contraction of the LAM in pregnancy has been associated with a prolonged active second stage of labour. 6,7Thus, detecting the presence of a paradoxical LAM contraction during the BDM in pregnancy is a logical assessment to be performed.A prolonged active second stage of labour has been linked to a greater incidence of LAM and anal sphincter trauma. 8,91][12] Minimising the time spent in the active second stage of labour is therefore an important variable in birth.Youssef et al. 7 suggest that, with correct instruction and biofeedback, a paradoxical LAM contraction during the BDM can be reversed.However, before clinical intervention can be discussed, a valid and reliable assessment of the BDM in pregnant women must be established.This study was designed to examine the concurrent validity and inter-rater reliability of vaginal palpation as a measure of the quality of the BDM in pregnant women, compared with TPUS.

| M ET HODS
Participants were recruited via an advertisement at The Physiotherapy Clinic, and via email to existing and current clients of The Physiotherapy Clinic.Participants volunteered to participate in the study.Consent forms were signed, and verbal consent was gained prior to the examination.Participants were included if they were in their third trimester of pregnancy.Participants were excluded if they had an active vaginal infection.Using Arifin's web-based sample size calculator for reliability studies, 13 our sample size planning indicated that a total of 19 observations would have an 80% power to detect an effect with a minimum acceptable kappa of 0.4, where α = 0.05.
The experiment took place inside a physiotherapy clinic, where three rooms were set up for each observer.Participants were numbered 1-20 and allocated an appointment time.Three participants were assessed at the same time, and rotated clockwise between rooms, ensuring randomness to who started with TPUS and who started with palpation.
Two experienced physiotherapists, with a minimum of 9 years of clinical experience in pelvic health physiotherapy, palpated the BDM via vaginal examination.The instructions for the BDM were consistent for each participant and were "bear down like you are opening your bowels".No instructions were given to either open or close their mouth, nose or glottis, no feedback was given on performance and no modifications were made to their technique.The instructions were given to the patient prior to attempting the BDM.Physiotherapists described the ability of the participants to bear down as contraction, no movement or lengthening of the LAM.The participants had two attempts, and the attempt most reflective of normal was recorded.
The same participants were assessed by a pelvic health physiotherapist with postgraduate training and clinical experience using TPUS spanning >4 years.The APD was measured during the BDM.The APD is a measure from the inferior border of the pubic bone to the anterior border of the puborectalis, at the anorectal angle.If the APD shortened by >2 mm, this was described as a contraction of the LAM.If the APD did not change or only shortened by up to 2 mm, this was described as no movement.If the APD lengthened by >2 mm, this was described as a lengthening of the LAM.For this study, as we defined the LAM during the BDM as contracted, no movement or lengthening, we felt that we needed a cut-off that defined no movement.Absolute zero is difficult to capture on real-time ultrasound.In a study measuring the inter-and intra-rater reliability of 2D TPUS, Bernard et al. found a standard error measure of the APD at rest to be 1.5 mm between two raters. 14Given that no movement could also be defined as a resting state, this information was assumed to be transferable.
The TPUS screen was turned away from the participants to avoid biofeedback.All observers were blinded to each other's results.All assessment and therefore the collection of data was performed on the same day.
The data were analysed using the statistical software R (The R foundation, Vienna, Austria).Descriptive statistics of the BDM were collected.In addition, the Fleiss kappa coefficient was used to test the agreement between raters.Agreement was defined as each observer describing each participant's BDM as being exactly the same.Exact agreement was deemed essential, as all three observations represent distinctly different physical presentations of the LAM.
Recruitment continued until we reached our target of 20 pregnant women in their third trimester of pregnancy.Seventeen of the 20 women were nulliparous; three were multiparous, two of whom had vaginal births and one of whom had a caesarean section.No participants were excluded.
Paradoxical contraction during the BDM was identified with TPUS in 6/20 participants.Of those six paradoxical contractions identified under TPUS, two were identified by one observer palpating the BDM and three were identified by the other observer palpating the BDM.All raters only agreed on 2/6 paradoxical contractions.No movement of the LAM was reported in 4/20 participants by one observer palpating the BDM, whereas the other observer palpating the BDM reported no findings of no movement of the LAM; 2/20 participants were found to have no movement of their LAM under TPUS.Exact agreement was found in 11/20 participants who lengthened their levator ani between one observer palpating the BDM and TPUS, whereas the other observer rated 16/20 as lengthening their levator ani.These raw data are represented in Table 1.

| DISCUS SION
In carrying out this study, and particularly designing the instructions for the BDM, multiple issues were discovered.Bearing down during the active second stage of labour is a highly debated topic.Despite extensive literature on the topic, it remains unclear how women should bear down during the active second stage of labour.Spontaneous pushing is defined as pushing in response to an undeniable urge to push. 15The urge to push felt by women happens as the fetal head makes contact with receptors in the LAM; a women given no instructions at this stage will bear down with a contraction, often vocalising as they do so. 15,16A woman who is directed or coached to push will be given a variety of instructions depending on the care provider, but directed pushing has not been shown to be advantageous over spontaneous pushing for maternal or neonatal outcomes. 15,16In theory, directed pushing with the mouth and nose closed is the Valsalva manoeuvre (VM).The LAM has been shown to contract and thus move caudally in response to traditional instructions for the VM. 2 During parturition, it is obvious that the pelvic floor should descend and lengthen with the pressure from the fetal head, thus regardless of the pushing being spontaneous or coached, one known variable is that the LAM should be lengthening. 2,17

| Main findings
This study was designed to analyse whether vaginal palpation of the BDM is a valid measure of the BDM in pregnant women, and if reliability exists between raters palpating the BDM.To the authors' knowledge, there have been no studies to determine the best way to analyse a pregnant woman's bearing-down technique.Measuring the APD using TPUS is accepted for this study as the most accurate measure of the BDM, as the image can be played back and measurements can be made slowly.During palpation, however, the assessor has only seconds to decide, rendering TPUS as having less room for error.In addition, the APD using TPUS has been used in previous literature analysing the BDM. 6,7lthough the majority of women in this study were assessed correctly via palpation, the number who were not does raise cause for concern.The observers in this study were experienced pelvic health physiotherapists, with experience in palpating the BDM.However, they did not agree on the score for every participant.This is perhaps not surprising given recent findings reported Davidson et al., 18 who found inconsistencies with palpation among physiotherapists, despite their level of experience.According to Fleiss, 19 a Fleiss kappa coefficient of <0.4 represents poor agreement beyond chance.The best Fleiss kappa coefficient between observers was 0.457, and thus only slightly better than poor agreement.Otherwise, all Fleiss kappa coefficients were <0.4,and thus it is clear that the agreement between raters is poor.Most concerning was the disagreement on when the LAM did shorten rather than lengthen, demonstrating the possibility that paradoxical LAM contraction during the BDM can be missed using palpation.This study did not find validity or inter-rater reliability when palpating the BDM in pregnant women compared with measuring the APD using TPUS.
The examiners who palpated the BDM raised a few points once the results were analysed to try to understand the results.One suggestion was that perhaps the downward pressure of high IAP reaching the pelvis without LAM lengthening could be confused for levator hiatal area opening.In addition, for some women perhaps the LAM changes throughout the BDM, with some lengthening and then with shortening within one BDM.These are interesting points and further research is required to determine whether this is the case.

| Strengths
This is the first study to look at the validity and inter-rater reliability of palpating the BDM.In light of recent research indicating that the BDM in pregnancy may be important as a possible predictor of a longer than desirable active second stage of labour, a valid assessment tool is necessary in the clinical setting.The study adhered to optimal experimental conditions, ensuring that the observers were blinded to each other's results, that the instructions given to each participant were exactly the same and that participants were blinded to their results.Each observer had been working full time in pelvic health physiotherapy for a minimum of 6 years, including using TPUS for a minimum of four of those 6 years.Each observer had numerous hours of postgraduate training, including both tertiary and non-tertiary-level education.All observers had been specifically trained in the use of real-time ultrasound.

| Limitations
It has long been known that the practice of a skill translates to motor learning. 20Given that the participants were allowed six opportunities to bear down in total, we could not fully limit skill acquisition occurring in patients.It is plausible that a participant assessed by examiner 1 had a paradoxical contraction of the LAM and that by the time they were assessed by examiner 3 they may have acquired the skill and learned to lengthen their LAM.We attempted to avoid the impact of learning by ensuring that participants were not given any feedback about their performance during the assessment.In addition, we randomised the starting position of each participant, in an attempt to disperse the impact of motor learning.One possible way to avoid motor learning in future studies would be to collect the data at different time points, as it has been shown that a delay between practice decreases motor learning. 21It is also plausible that fatigue may have changed a participant's performance.In clinical practice we observe that many people report not liking the feeling of bearing down, and thus by the third examiner a participant may have been bearing down with poorer technique.A follow-up study giving participants more time between observers may influence the results.

| Interpretation
Physiotherapists are generally accustomed to using their hands to palpate muscle tone, strength and function.This study has shown that caution must be taken when assessing the BDM using palpation alone.Where possible, and particularly in the case where the examiner is unsure of LAM movement, the authors strongly recommend examining the APD under TPUS.The valid assessment of the BDM antenatally is important, as Youssef et al. have shown that with instruction and practice a women's BDM technique can improve prior to birth, 7 and, as these authors and others have shown, this may influence their length of second stage. 6,7

| CONCLUSION
Although the assessment of the BDM is a clinically important assessment, this study did not find vaginal palpation of the BDM in pregnant women to have concurrent validity or inter-rater reliability.The BDM in pregnant women prior to vaginal birth should be assessed using the APD with TPUS, where possible, particularly in the case where vaginal palpation is inconclusive or no movement is palpated.

AU T HOR C ON T R I BU T ION S
JM-W was the lead author in the conception, design and planning of the study, in data collection and in writing up.IN and SD-VS have played a role in the conception of this project, and in planning and editing the article.EB and TW played a role in the conception and planning of the study, and carrying out data collection.

AC K NO W L E D GE M E N T S
The authors would like to acknowledge the participants of the study, for donating their time.The authors would also like to acknowledge Dr Andrew Woodward from the University of Canberra, Faculty of Health, for his expertise in data and statistical analysis.Open access publishing facilitated by University of Canberra, as part of the Wiley -University of Canberra agreement via the Council of Australian University Librarians.

F U N DI NG I N FOR M AT ION
This was a self-funded study.

C ON F L IC T OF I N T E R E S T S TAT E M E N T
There are no interests to disclose.

DATA AVA I L A BI L I T Y S TAT E M E N T
The data that support the findings of this study are available on request from the corresponding author.The data are not publicly available owing to privacy or ethical restrictions.

E T H IC S A PPROVA L
Ethics approval for this project, including the use of human subjects, was approved by the human research ethics committee from The University of Canberra (no.9155) on 23 August 2022.

T A B L E 1
Frequency data for levator ani behaviour during the bearing-down manoeuvre (BDM) per observer.