Assessing feasibility and maternal acceptability of a biomechanically-optimized supine birth position: A pilot study.

BACKGROUND: In order to manage a protracted second stage of labor, "eminence-based" birth positions have been suggested by some healthcare professionals. Recent biomechanical studies have promoted the use of an optimized supine birthing position in this setting. However, uncertainty exists regarding the feasibility of this posture, and its acceptability by women. This pilot study primarily aimed to assess these characteristics. OBJECTIVE AND METHODS: In this monocentric prospective study, 20 women with a protracted second stage of labor were asked to maintain a biomechanically-optimized position for at least 20 minutes at full dilatation. This posture is similar to the McRoberts' maneuver. Maintaining the position for 20 minutes or more was considered clinically relevant and indicative of feasibility and acceptability. Satisfaction with the position was assessed using a Visual Analogue Scale (VAS). A sub-group analysis was performed to assess eventual differences between more and less satisfied patients, according to the median of patients' satisfaction scores.
RESULTS: Seventeen patients (85%) maintained the optimized position for at least 20 minutes. The median satisfaction score of these participants was 8 (interquartile range: 1) out of 10. No significant differences were found between the two sub-groups (satisfaction score <8 vs satisfaction score ≥8) regarding general and obstetric characteristics, as well as obstetrical and fetal outcomes.
CONCLUSION: The optimized position is acceptable and feasible for women experiencing a protracted second stage of labor. Further clinical studies are needed to assess the efficiency of such positions when women undergo an obstructed labor.

Introduction

The increased rate of cesarean section in developed countries is a worrying public health problem. According to the World Health Organization, there is no reduction in maternal morbidity and mortality at rates greater than 10–15%, a threshold largely exceeded in developed countries [1]. Nearly 20% of cesarean sections are performed in response to an obstructed labor after a protracted second stage of labor, corresponding to when the fetus does not engage in the pelvis despite a fully dilated cervix [2]. This highlights the need for further research on childbirth biomechanics, which could elucidate the mechanism behind such obstructions and point to more favorable birthing positions.

In order to manage protracted labor, some healthcare professionals have suggested adopting “eminence-based” positions for giving birth. Eminence-based medicine, as opposed to evidence-based medicine, refers to clinical practices relying entirely on the opinion and experience of health professionals, rather than on scientific research. Recently, there is growing evidence recognizing that eminence-based positions can optimize the alignment between the birth canal (formed by pelvic bones, lumbar spine and soft pelvic tissues) and the fetus [3-5]. Some positions may promote fetal descent through the pelvic inlet (the anatomical limit between the false and true pelvis, bounded anteriorly by the pubic symphysis, laterally by the iliopectineal lines, and posteriorly by the sacral promontory) more efficiently than others [3-5]. In theory, an optimal birth position can be biomechanically defined as a position where the pelvic inlet is perpendicular to the lumbar spine, while minimizing lumbar lordosis i.e. achieving a sort of ‘‘obstetric chute” [3-5]. Recent research in experimental settings (i.e. not during labor), using an optoelectronic motion capture system, suggested a specific position which approaches the biomechanical ideal mentioned above [3-5]. This method involves a squatting position in a supine set-up i.e. lying on one’s back with a 30 degree angle from horizontal, legs in abduction with maximal hip flexion and minimizing lumbar lordosis (Fig 1). However, this mechanistic approach to childbirth based only on biomechanics is insufficient, as other factors at play during childbirth and the clinical impact of such positions have yet to be assessed [6, 7]. Consequently, there is a need to determine the feasibility of optimized positions in clinical settings to ensure that fundamental biomechanical research can be applied, especially during labor dystocia [6]. The acceptability of biomechanically-optimized positions should also be evaluated as these more complex positions could make a parturient feel restrained in their experience of giving birth.

Fig 1

Illustration of the biomechanically-optimized supine position assessed in this study.

This prospective pilot interventional study primarily aimed to assess the feasibility and acceptability for parturients of a biomechanically-optimized birth position. We hypothesize that participants can maintain the optimized birth position, resembling the posture obtained at the end of a McRoberts’ maneuver [6, 8], for at least 20 minutes without feeling uncomfortable. In addition, for the women who maintained the position for at least 20 minutes, we investigated if population characteristics, obstetrical conditions and obstetrical outcomes differed between women reporting higher and lower satisfaction.

Materials and methods

Study population

Participants gave birth at a tertiary university hospital (Lausanne University Hospital) between August 2019 and December 2019. Eligible participants were recruited during their antenatal consultation in our outpatient clinic or before induction of labor for non-emergency indications (post-term, oligoamnios, prelabor rupture of membranes) at greater than 39 weeks of gestation. To be eligible, women had to have been diagnosed with a protracted second stage of labor, i.e. those whose fetus did not engage in the pelvic inlet after one hour at full cervical dilation. Exclusion criteria included physical incapacity or medical contraindications precluding the intervention (e.g. orthopedic injury or disease preventing the parturient from adopting the optimized position), clinically significant concomitant diseases, incapacity of judgment, inability to follow the procedures of the study due to language barriers/psychological disorders and non-reassuring fetal heart monitoring or abnormal bleeding during labor.

The study protocol was approved by the local Institutional Review Board (Ethical Commission of the Canton of Vaud, Switzerland, 2019–00872) and declared on ClinicalTrials.gov portal: NCT04056793 (14/08/2019). All experiments were performed in accordance with relevant Ethics Committee and relevant Swiss guidelines and regulations. All participants provided written informed consent. Also, the individual in Fig 1 gave written informed consent (as outlined in PLOS consent form) to publish this photograph. No financial incentive was offered for participation. A physician independent of the research team performed data monitoring and quality assurance.

Intervention

When a protracted second stage of labor occurred, the parturient was asked to adopt the biomechanically-optimized birth position with the help of a midwife. The optimized position performed in this study was previously defined and biomechanically assessed by our team [3]. This supine position combined maximal flexion and abduction of the hip joints with minimizing lumbar lordosis, using foot rests to correctly position the legs (Fig 1) [3]. Participants were invited to maintain this position for 20 minutes. This period of time was selected because it represents approximately 10 uterine contractions and we considered that such a duration would allow us to appreciate the effectiveness of the intervention without being too constraining for participants. This duration was also selected because two-thirds of women in our hospital request epidural analgesia and it is not recommended to make them adopt such a position for a prolonged amount of time, in order to avoid any risk of malposition or nerve compression [9]. Women were free to change position at any time, or they could maintain it for more than 20 minutes if they so wished. The study did not change the usual management of dystocia, in particular the administration of oxytocin after 1 hour without progression of the presentation at the second stage of labor (protracted second stage of labor).

Outcomes

The primary outcome was to assess the feasibility of the optimized position, evaluated according to the duration the participants could maintain it. Specifically, the position was considered feasible for a participant when the participant maintained it for at least 20 minutes. The secondary objective was to assess the acceptability (subject satisfaction and pain perceived) of the optimized position.

We used the VAS (Visual Analogue Scale) to evaluate participants’ satisfaction regarding the position, ranging from 0 (no satisfaction) to 10 (complete satisfaction). An interview was conducted by one of the authors (LB) during the two days following delivery, where a standardized question was asked of all the participants: “Could you report your satisfaction about the optimized position that was proposed to you on this visual scale”. The occurrence of pain related to the position was also recorded. A two-day time frame was chosen as it allowed patients to accurately recall their satisfaction concerning the optimized position without the study being too intrusive.

A sub-group analysis was performed to compare population characteristics, obstetrical conditions and obstetrical outcomes between the women with higher satisfaction scores and those with lower satisfaction scores. To this end, the participants who could maintain the posture for at least 20 minutes were divided in two sub-groups using the median satisfaction score as a cut-off. Data concerning risk factors of non-engagement of the fetus at full dilation, delivery outcome, fetal outcome and occurrence of eventual adverse events, such as symphysis pubis diastasis or maternal peripheral nerve disorders, were also collected. Perineal tears are reported according to the Royal College of Obstetrician and Gynecologist (RCOG) classification [10].

Statistical analysis

Power calculations were performed. We hypothesized that future studies involving newly developed technology focusing on the optimization of birth posture should be acceptable and feasible if 80% of participants could maintain a specific position for 20 minutes while giving birth. We estimated that 20 women would provide a power of at least 80% to detect a relative difference of 75% or greater in the incidence of the primary outcome (i.e. 80% of women maintaining the optimized position and 20% who did not tolerate it), with a 5% two-sided type I error. According to recent data, protracted labor at full dilatation affects 2.7% of women [11]. We estimated that 5 months would been necessary to complete this study in our maternity unit (average of 250 births per month).

Statistical distribution of quantitative variables was assessed with a Shapiro-Wilk test. In view of the non-normal distribution of the data, results are reported as medians and interquartile ranges (IQR) for numeric variables or as numbers and percentages for categorical variables. For quantitative variables, the statistical significance of the differences between the sub-groups was tested using Wilcoxon rank-sum tests. For qualitative variables, p-values were calculated using a multilevel mixed-effects linear regression. The significance level was defined as p < 0.05. Data analysis and reporting were performed using Stata V16 (Stata Corp, College Station, TX, USA).

Results

During the study period, 891 women were screened, out of which 20 were included (2.2%) (Fig 2). The median age of the participants was 33 (IQR: 7.5) years, and the median gestational age at labor was 40 (IQR: 2) weeks. Ninety percent of patients were nulliparous. Of the 20 patients included in the study, 13 (65%) had fetuses in the left and 7 (35%) in the right occiput anterior position. All women had epidural analgesia at some point before testing the biomechanically-optimized posture and 4 of them additionally had spinal anesthesia due to inadequate pain relief (Table 1).

Fig 2

Flow chart.

Table 1

Demographic and obstetrical characteristics just before adopting the biomechanically-optimized position.

Study population (n = 20)
Population characteristics
Maternal age (years)	33 [7.5]
Nulliparous	18 (90%)
Gestational age (weeks)	40 [2]
BMI (kg/m2)	23.5 [5.2]
Maternal height (cm)	161.5 [10.5]
Maternal weight (kg)	64.5 [16.2]
Obstetrical conditions
Oxytocin (UI)	1.5 [2]
SFH (cm)	35.5 [3]
Induction of labor	16 (80%)
AROM	7 (35%)
Cephalic presentation
LOA	13 (65%)
ROA	7 (35%)
Regional analgesia	20 (100%)
Spinal anesthesia	4 (20%)
Fetal macrosomia suspicion	4 (20%)

All data shown as n (%) or median [IQR].

BMI: Body mass index, SFH: Symphysis-Fundal Height, AROM: Artificial Rupture of Membranes, LOA: Left.

Occipito-Anterior, ROA: Right Occipito-Anterior.

Seventeen women (85%) stayed in the optimized position for a minimum of 20 minutes. One woman could not maintain the position for more than 5 minutes due to pain related to fetal engagement. A second woman discontinued after 10 minutes due to non-reassuring fetal heart rate. A third participant could not maintain the position for more than a few seconds due to low back pain related to labor that increased in any supine position. Specific pain/discomfort associated with the optimized position occurred in 2 participants (11.8%).

Among the 17 participants who maintained the optimized position for at least 20 minutes, the median satisfaction score was 8 (IQR: 1) out of 10. Neither maternal peripheral nerve dysfunction nor symphysis pubis diastasis were reported in any of these patients. Regarding obstetrical outcomes, 14 women achieved a spontaneous vaginal delivery (82.3%), 2 women underwent cesarean section (11.7%) and 1 woman required assisted delivery using forceps for non-progression of the presentation (5.9%). At the time of birth, the median Apgar score of the babies at 1, 5 and 10 minutes was 8.5, 9.5 and 10 (IQR: 2–1.5–0.5) respectively. Their median weight and head circumference were respectively 3610 (IQR: 520) g and 35 (IQR: 1.5) cm (Table 2).

Table 2

Outcomes for the 17 women who maintained the optimized position for at least 20 minutes.

Study population (n = 17)
Biomechanically-optimized position outcomes
Duration (min)	26.2 [5]
Satisfaction score (from 0 to 10)	8 [1]
Reported pain	2 (11.8%)
Obstetrical outcomes
Spontaneous delivery	14 (82.3%)
Instrumental delivery	1 (5.9%)
Caesarean section	2 (11.7%)
Perineal tears (RCOG Classification)
0	6 (37.5%)
1	1 (6.2%)
2	8 (50%)
3	1 (6.2%)
Fetal outcomes
Apgar score (from 0 to 10) at:
1 minute	8.5 [2]
5 minutes	9.5 [1.5]
10 minutes	10 [0.5]
Weight (g)	3510 [520]
Head circumference (cm)	35 [1]

All data shown as n (%) or median [IQR].

RCOG: Royal College of Obstetricians and Gynaecologists.

Comparisons of population characteristics, obstetrical conditions and obstetrical outcomes between the women with higher and lower satisfaction scores regarding the optimized position (median satisfaction score of VAS = 8 used as cut-off) are reported in Table 3.

Table 3

Comparison of population characteristics, obstetrical conditions and obstetrical outcomes between women with higher and lower satisfaction scores regarding the optimized position.

Study population (n = 17)	Satisfaction score <8	Satisfaction score ≥ 8	p-value
	n = 8	n = 9
Population characteristics
Maternal age (years)	30 [9]	33 [5]	0.4
Nulliparous	8 (100%)	8 (88.9%)	0.3
Gestational age (weeks)	40 [2]	40 [1]	0.2
BMI (kg/m2)	23.6 [8.5]	23.3 [4.4]	0.6
Maternal height (cm)	160 [8]	163 [8]	0.7
Maternal weight (kg)	59 [23.5]	67 [9]	0.7
Obstetrical conditions
Oxytocin (UI)	1.7 [1.2]	1.7 [3.8]	0.8
SFH (cm)	35 [4]	36 [2]	0.7
Induction of labor	7 (87.5%)	6 (66.7%)	0.3
AROM	2 (25%)	3 (33.3%)	0.7
Cephalic presentation
LOA	4 (50%)	6 (66.7%)	0.5
ROA	4 (50%)	3 (33.3%)
Epidural analgesia	8 (100%)	9 (100%)	1.0
Spinal anesthesia	0 (0%)	3 (33.3%)	0.7
Fetal macrosomia suspicion	0(0%)	3 (33.3%)	0.7
Optimized position outcomes
Duration (min)	20 [2.5]	25 [10]	0.3
Reported pain	2 (25%)	0 (0%)	0.08
Satisfaction score (from 0 to 10)	7 [1]	8 [1]	n/a
Obstetrical outcomes
Spontaneous delivery	7 (87.5%)	7 (77.8%)	0.8
Instrumental delivery	0 (0%)	1 (11.1%)
Cesarean section	1 (12.5%)	1 (11.1%)
Perineal tears (RCOG classification)
0	2 (28.5%)	4 (44.4%)	0.25
1	0 (0%)	1 (11.1%)
2	4 (57.1%)	4 (44.4%)
3	1 (14.3%)	0 (0%)
Fetal outcomes
Apgar score (from 0 to 10)
1 minute	8 [4]	9 [2]	0.5
5 minutes	10 [4]	9 [1]	0.8
10 minutes	10 [2]	10 [0]	0.1
Weight (g)	3350 [360]	3700 [380]	0.18
Head circumference (cm)	34.5 [1.4]	35 [1.3]	0.3

All data shown as n (%) or median [IQR].

BMI: Body mass index, SFH: Symphysis-Fundal Height, AROM: Artificial Rupture of Membranes, LOA: Left Occipito-Anterior, ROA: Right Occipito-Anterior.

No significant differences were found between the two sub-groups regarding general and obstetric characteristics, obstetrical and fetal outcomes or occurrence of specific pain related to the optimized position (p ≥ 0.08).

Midwives who positioned participants did not report any issue concerning the study’s completion, being already experienced in advising various positions when a mechanical dystocia occurs and in helping patients to adopt them. Therefore, the intervention did not interfere with global patient care.

Discussion

Most of the participants (85%) could maintain the biomechanically-optimized position for at least 20 minutes, with a good satisfaction score (VAS median score at 8 out of 10). Pain specifically related to this position occurred only in a minority of cases. No dysfunction of peripheral nerves nor symphysis pubis diastasis were reported in any of the patients. Therefore, it seems that this prospective pilot study confirmed the hypothesis that an optimized position resembling squatting while lying supine, similar to that obtained at the end of a McRoberts’ maneuver [3, 5], is feasible and well accepted by women in labor. Furthermore, there was no difference in participant characteristics between the women reporting higher and lower levels of satisfaction.

A high percentage of nulliparous participants emerged in the population characteristics (90%). This could be explained by a noticeably longer second stage of labor in nulliparous women and by a higher prevalence of mechanical dystocia in this population (16.5% of nullipara versus 9.9% of multipara) [12, 13]. Naturally, engagement of the fetus and childbirth in parous women occurred more frequently before one hour of full cervical dilatation.

Another factor associated with higher risk of obstructed labor is the presence of an occiput posterior position [14]. Interestingly, in our cohort, fetuses in the occiput anterior position at time of birth were over-represented in comparison to the rates at full dilatation reported in the literature [14-17]. Per the protocol in place at our hospital, manual rotation of occiput posterior positions is only performed after one hour of full dilation. Despite the occurrence of obstructed labor, all participants had fetuses in «spontaneous» occiput anterior positions.

According to the Swiss Federal Statistical Office, rates of emergency cesarean section and instrumental deliveries in Switzerland reached 15.8% and 11.1% respectively in 2017 [18]. Therefore, this small sample size study seemed consistent with usual practice: it did not illustrate abnormal rates of cesarean section or assisted delivery. Our study was not designed to assess the impact of this position on the means of delivery, but the results it provided motivate further studies to address this question.

One limitation of this study is that no reference value differentiating between a birth position judged satisfactory or unsatisfactory by the parturient is available in the literature. In light of this limitation, we chose the median of the satisfaction score to compare women with higher and lower satisfaction. This approach nonetheless allows us to draw a parallel between our results and previous randomized trials which reported maternal satisfaction with position during labor in order to correct occiput posterior fetal position [15–17, 19]. This indicates that the acceptability of the biomechanically-optimized position in this study is at least comparable to the results reported in prior works [15–17, 19]. Another limitation of this study concerns the small size of our cohort, which didn’t allow us to adjust potential confounding factors for satisfaction and acceptability (parity, duration of labor).

Despite these limitations, our results are already consistent enough to confirm that the biomechanically-optimized position presented in this study is suitable and should be further assessed. Additionally, to improve the assessment of the birthing position, it would be useful to consider other evaluation criterion, such as the progression of the fetus in the pelvic inlet. Furthermore, computational models could also provide crucial insights on the different biomechanical aspects of such positions [20]. Indeed, such models could inform us on the efficacy of the positions and constitute a valid step before conducting large interventional studies [6, 21]. Future studies should also focus on the factors impacting the acceptability and satisfaction of the optimized position. For instance, it would be useful to understand the role of pain relief and its effect on the sense of self-empowerment. Better understanding of the factors related to acceptability and satisfaction is important, to avoid solutions exclusively based on biomechanics and therefore potentially disempowering to women’s experience during delivery [22]. Labor ward caregivers must then endeavor to cultivate maternal instincts and advocate non-intervention in normal processes [22]. Nonetheless, whether instinctively adopted or not, it remains important to understand why some postures are more favorable than others.

Conclusion

The majority of our participants were able to maintain the biomechanically-optimized birthing position for a duration considered to be clinically relevant, without side effects. Therefore, this position can be considered as feasible and acceptable for women giving birth. These findings call for additional biomechanical and interventional studies to determine if this optimized position is an efficient solution to obstructed labor.

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14 Apr 2021

PONE-D-20-31050

Feasibility and acceptability assessment of a biomechanically-optimized supine birth position: A pilot study

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Reviewer #1: This manuscript reports observed results from a pilot study investigating feasibility and acceptability of a biomechanically-optimized supine birth position. I have below questions and comments for statistical analysis.

The description is not clear for power calculation. Please provide detail for the hypotheses. What will you compare to 80%?

For qualitative variable, why was a multilevel mixed-effects linear regression used? If the qualitative variable is categorical, frequency table and Chi-squared test or Fisher’s exact test may be used.

Reviewer #2: Thanks for giving me such a valuable chance to review this paper. This paper addressed an important issue in maternity care and is very well-written. The authors assessed the feasibility and maternal acceptability of a biomechanically-optimized supine birth position. Similar studies on this topic are limited; Thus this study has academic significance. On the other hand, This study also provides valuable insights into dealing with obstructed labor.

On the whole, I only have a few suggestions for revision. Comments are as following. I would be delighted to recommend this paper for publication after a minor revision.

Background:

#1 What are“eminence-based” positions? Any examples?

#2 “ there is growing evidence recognizing that such management can improve the alignement between the birth canal (formed by pelvic bones, lumbar spine and soft pelvis tissues) and the fetus.”

Please consider adding references to support this statement.

#3As is stated in the Background section, “a particular position, similar to squatting while lying on the back” could optimize delivery.

How does this position optimize delivery? In what manner? By improving the alignement between the birth canal? I believe a brief explanation may add values.

Material and method

#4 Who performed the interview two days after delivery? Any rationale for choosing this date to conduct the interview?

“standardized question was ask to all the participants during an interview that took place during the two days following the delivery.

Discussion

#5 It would be better to add a reference for the numbers

“According to the Swiss Federal Statistic Office, rates of emergency cesarean section and instrumental deliveries in Switzerland reached respectively 15.8 % and 11.1 % in 2017”

Reviewer #3: General Notes:

-- The position is not McRobert position -- it is McRoberts' position (or McRoberts' maneuver). It was named for Dr. William McRoberts. It can be written without the possessive apostrophe, if desired -- but the s is required.

-- Information on how this position was maintained (e.g. use of foot rests) would be helpful (referring to Figure). Those who understand McRoberts' position normally expect it to be maintained by two assistants/family members (one on each leg).

-- While you refer to your papers on an optimal birth position, it would be very helpful to provide a little more detail in the Introduction of this paper about the findings in those papers. What is the necessary angle of the pelvis? How did you define optimized? How is it different in angles from lithotomy?

Substantive Corrections or Clarifications:

INTRODUCTION:

-- I am not sure what you mean by "the pelvic inlet plan" -- please clarify

RESULTS:

-- what is "important back discomfort"?

-- it appears from the Results section that when you discussed peripheral nerve disfunction, that you were thinking about maternal nerves. This should be clarified in the Methods section (outcomes paragraph). Readers familiar with the fetal risk factors associated with labor dystocia and the typical use of McRoberts' maneuver in shoulder dystocia events may assume that the description refers to neonatal nerve injuries.

-- I would suggest putting a percent sign in the parenthetical values of Table 1 to remind readers what you are signifying, as it is a bit hard to ascertain when first looking at the table.

-- I would suggest separating out the 3 time points for Apgar scores onto three separate lines in Table 2 and Table 3. This will clarify it for readers.

DISCUSSION:

-- in your paragraph discussing the limitation due to the lack of a literature value on position, I originally thought that you were talking about the McRoberts' position. You should clarify in this sentence that you are discussing the subjects' opinions regarding their satisfaction with the position.

-- You say that you are comparing your results to randomized trials related to effectiveness of various positions (refs 14-17). However, you have not reported on any data regarding effectiveness -- only patient satisfaction. If there are specific data that you are comparing to (e.g. patient satisfaction with the positions used in those studies), please cite that data and clearly describe the comparison.

-- "while further studies are necessary to precise the numbers" is not grammatically correct - and I am not sure exactly what you are trying to say. Increasing the numbers would allow you to statistically differentiate between narrower groups -- but it is not likely to increase the precision of your measurements. Please write this section more clearly to differentiate between actual measurements and statistical conclusions.

Grammatical Corrections (NOTE: There are additional grammar errors that I did not note. Please have the document reviewed by a proficient writer whose first language is English to minimize errors.)

ABSTRACT:

-- it is most common to refer to the second stage as "second stage OF labor" rather than without the preposition

-- "is similar to the McRobert maneuver" should be "is similar to the McRoberts' maneuver"

-- In "A sub-group analyses was performed according to the median of the patient satisfaction score, to assess eventual differences between more and less satisfied patients," analyses should be ANALYSIS and the comma should be deleted between "score" and "to"

INTRODUCTION:

-- "threshold largely exceeded in developed countries" should be preceded by "a" as in "a threshold largely exceded..."

-- change "approach of childbirth" to "approach to childbirth"

-- delete "in future researches." If you really want to keep it (it doesn't make sense), it should be "in future research."

-- "can be transfer to" should be "can be transferred to"

-- "could make parturient feel" should be "could make a parturient feel"

-- "resembling at the posture" should be "resembling the posture"

MATERIALS AND METHODS:

-- "prelabor rupture of membrane" should be "prelabor rupture of membranes"

-- "whose fetus did not engage" should be "those whose fetus ..."

-- in the discussion of the IRB approval, there should be no comma between the IRB protocol number and "and" [i.e. -00872) and declared] and there should be no period at the end of ClinicalTrials.gov

-- "would allow to appreciate the effectiveness of the intervention without being to constraining for the women" should be "would all us to appreciate ... without being too constraining ..."

-- "the primary outcomes" should be "the primary outcome"

-- if you want to include the comma in the first sentence about outcomes, then you need a subject in the second phrase (i.e. "and this was evaluated.")

-- "to evaluate participant's satisfaction" should be either "to evaluate a participant's satisfaction" or "to evaluate participants' satisfaction"

-- "A standardized question was ask to all" should be "A standardized question was asked of all"

-- "obstetrical conditions and obstetrical outcomes between women the women with higher satisfaction to the women with lower satisfaction" should be "obstetrical conditions and obstetrical outcomes between the women with higher satisfaction and the women with lower satisfaction."

-- "Data concerning risks factor of non-engagement" should be "Data concerning risk factors of non-engagement" and "peripheral nerves disorders" should be "peripheral nerve disorders"

-- "Shapiro-wilk test" should be "Shapiro-Wilk test" as it refers to a name (or pair of names)

RESULTS:

-- "median weight and head circumference were respectively of 3610" should be "median weight and head circumference were respectively 3610"

-- "They are used to suggest various positions when a mechanical dystocia occurs and to help patients adopting them" should be "They are used to suggesting various positions when a mechanical dystocia occurs and to helping patients to adopt them."

DISCUSSION:

-- "there were no difference in participants’ " should be either "there were no differences in participants'" or "there was no difference ..."

-- "This study was not design" should be "This study was not designed"

-- "A limitation of this study consists in the absence of a reference value in the literature to differentiate between a position judged satisfactory or unsatisfactory" should be "A limitation of this study includes the absence of a reference value ..."

-- "this could inform about the efficiency" should be "this could inform about the efficacy" (or effectiveness)

-- "the role pain relief" should be "the role of pain relief" and I am not sure from the rest of that sentence exactly what you are saying, but could it be "the role of pain relief and its effect on the sense of self-empowerment."

Reviewer #4: Since it is stated that future biomechanical studies will be needed, the usage of computational biomechanics is already a reality, which should be recognized in the present paper, for example with the following reference

Borges, M., Moura, R., Oliveira, D., Parente, M., Mascarenhas, T., & Natal, R. (2021). Effect of the birthing position on its evolution from a biomechanical point of view. Computer Methods and Programs in Biomedicine, 200doi:10.1016/j.cmpb.2020.105921

The description given on the text for the position used on the study is too vague. Improve the following sentence:

“Recent research in experimental settings, i.e. not during labor, suggested a particular position, similar to squatting while lying on the back (hyperflexion of the thighs and loss of the lumbar lordosis) (cf. Figure 1), could optimize delivery [3-5]”

No information is given in relation to the women, in relation to their body mass index, height, weight, etc. This information is relevant.

**********

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Reviewer #1: No

Reviewer #2: No

Reviewer #3: No

Reviewer #4: No

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15 Jun 2021

Editorial office of Plos one

5th June 2021

Ref.: “ Assessing feasibility and maternal acceptability of a biomechanically-optimized supine birth position : A pilot study”

Dear Editorial Board Member,

We would like to thank the reviewers for the assessment our manuscript which will improve the scientific quality of our study. Please find attached the revised manuscript, with changes highlighted using the tracked changes mode in Word. We considered each suggestion from the reviewers, and you may find below our responses to their comments.

Journal requirements:

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https://journals.plos.org/plosone/s/file?id=ba62/PLOSOne_formatting_sample_title_authors_affiliations.pdf

The format of the manuscript was modified according to the guidelines

2. Please review your reference list to ensure that it is complete and correct. If you have cited papers that have been retracted, please include the rationale for doing so in the manuscript text, or remove these references and replace them with relevant current references. Any changes to the reference list should be mentioned in the rebuttal letter that accompanies your revised manuscript. If you need to cite a retracted article, indicate the article’s retracted status in the References list and also include a citation and full reference for the retraction notice.

We reviewed all of our references. To our knowledge no article were retracted.

3. We note that you have indicated that data from this study are available upon request. PLOS only allows data to be available upon request if there are legal or ethical restrictions on sharing data publicly. For information on unacceptable data access restrictions, please see http://journals.plos.org/plosone/s/data-availability#loc-unacceptable-data-access-restrictions.

In your revised cover letter, please address the following prompts:

a) If there are ethical or legal restrictions on sharing a de-identified data set, please explain them in detail (e.g., data contain potentially identifying or sensitive patient information) and who has imposed them (e.g., an ethics committee). Please also provide contact information for a data access committee, ethics committee, or other institutional body to which data requests may be sent.

The data underlying the findings cannot be made freely available because of ethical and legal restrictions. An important number of variables included in this study that put together could be used to re-identify the participants. Therefore, the Swiss Association of Research Ethics Committees strictly forbids making such data freely available. However, they can be obtained upon request. Readers may contact: david.desseauve@chuv.ch to request the data.

b) If there are no restrictions, please upload the minimal anonymized data set necessary to replicate your study findings as either Supporting Information files or to a stable, public repository and provide us with the relevant URLs, DOIs, or accession numbers. Please see http://www.bmj.com/content/340/bmj.c181.long for guidelines on how to de-identify and prepare clinical data for publication. For a list of acceptable repositories, please see http://journals.plos.org/plosone/s/data-availability#loc-recommended-repositories.

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The data cannot be freely available for the reasons mentioned in the above statement. Data access can be only possible after scientific assessment and data

sharing agreement, detailing the type of data requested.

4. Please amend either the title on the online submission form (via Edit Submission) or the title in the manuscript so that they are identical.

We have homogenised the title in the both documents

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We did not provide any Supporting Information file

6. We note that Figure 2 includes an image of a participant in the study.

As per the PLOS ONE policy (http://journals.plos.org/plosone/s/submission-guidelines#loc-human-subjects-research) on papers that include identifying, or potentially identifying, information, the individual(s) or parent(s)/guardian(s) must be informed of the terms of the PLOS open-access (CC-BY) license and provide specific permission for publication of these details under the terms of this license.

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Please amend the methods section and ethics statement of the manuscript to explicitly state that the patient/participant has provided consent for publication: “The individual in this manuscript has given written informed consent (as outlined in PLOS consent form) to publish these case details”.

If you are unable to obtain consent from the subject of the photograph, you will need to remove the figure and any other textual identifying information or case descriptions for this individual.

The participant in the photograph signed the consent form. We amended the methods section and ethics statement of the manuscript on line.

Reviewer comments to the author

Reviewer #1: This manuscript reports observed results from a pilot study investigating feasibility and acceptability of a biomechanically-optimized supine birth position. I have below questions and comments for statistical analysis.

The description is not clear for power calculation. Please provide detail for the hypotheses. What will you compare to 80%?

We clarified our calculation for power (line 469-471).

For qualitative variable, why was a multilevel mixed-effects linear regression used? If the qualitative variable is categorical, frequency table and Chi-squared test or Fisher’s exact test may be used.

We used this statistical model as data was not distributed normally.

Reviewer #2: Thanks for giving me such a valuable chance to review this paper. This paper addressed an important issue in maternity care and is very well-written. The authors assessed the feasibility and maternal acceptability of a biomechanically-optimized supine birth position. Similar studies on this topic are limited; Thus this study has academic significance. On the other hand, This study also provides valuable insights into dealing with obstructed labor.

On the whole, I only have a few suggestions for revision. Comments are as following. I would be delighted to recommend this paper for publication after a minor revision.

Background:

#1 What are“eminence-based” positions? Any examples?

More information was provided (line 127-129)

#2 “ there is growing evidence recognizing that such management can improve the alignement between the birth canal (formed by pelvic bones, lumbar spine and soft pelvis tissues) and the fetus.”

Please consider adding references to support this statement.

The references were added (line 131).

#3As is stated in the Background section, “a particular position, similar to squatting while lying on the back” could optimize delivery.

How does this position optimize delivery? In what manner? By improving the alignement between the birth canal? I believe a brief explanation may add values.

This was clarified as requested (line 129-141).

Material and method

#4 Who performed the interview two days after delivery? Any rationale for choosing this date to conduct the interview?

“standardized question was ask to all the participants during an interview that took place during the two days following the delivery.

These questions were answered (line 399-404).

Discussion

#5 It would be better to add a reference for the numbers

“According to the Swiss Federal Statistic Office, rates of emergency cesarean section and instrumental deliveries in Switzerland reached respectively 15.8 % and 11.1 % in 2017”

The reference was included as suggested (line 755).

Reviewer #3: General Notes:

-- The position is not McRobert position -- it is McRoberts' position (or McRoberts' maneuver). It was named for Dr. William McRoberts. It can be written without the possessive apostrophe, if desired -- but the s is required.

The correction was made throughout the manuscript.

-- Information on how this position was maintained (e.g. use of foot rests) would be helpful (referring to Figure). Those who understand McRoberts' position normally expect it to be maintained by two assistants/family members (one on each leg).

Mention of foot rests was included in the study population section (line 336).

-- While you refer to your papers on an optimal birth position, it would be very helpful to provide a little more detail in the Introduction of this paper about the findings in those papers. What is the necessary angle of the pelvis? How did you define optimized? How is it different in angles from lithotomy?

This was added to the manuscript (line 129-141)

Substantive Corrections or Clarifications:

INTRODUCTION:

-- I am not sure what you mean by "the pelvic inlet plan" -- please clarify

The sentence was clarified (line 132-134)

RESULTS:

-- what is "important back discomfort"?

This part was replaced by “low back pain related to labor and increased in any supine position” to increase precision (line 576-577).

-- it appears from the Results section that when you discussed peripheral nerve disfunction, that you were thinking about maternal nerves. This should be clarified in the Methods section (outcomes paragraph). Readers familiar with the fetal risk factors associated with labor dystocia and the typical use of McRoberts' maneuver in shoulder dystocia events may assume that the description refers to neonatal nerve injuries.

This was clarified by adding the adjective “maternal” before “peripheral nerve dysfunction” (line 461).

-- I would suggest putting a percent sign in the parenthetical values of Table 1 to remind readers what you are signifying, as it is a bit hard to ascertain when first looking at the table.

The modification was made as suggested for all the tables.

-- I would suggest separating out the 3 time points for Apgar scores onto three separate lines in Table 2 and Table 3. This will clarify it for readers.

The modification was made as well.

DISCUSSION:

-- in your paragraph discussing the limitation due to the lack of a literature value on position, I originally thought that you were talking about the McRoberts' position. You should clarify in this sentence that you are discussing the subjects' opinions regarding their satisfaction with the position.

This was clarified as requested (line 760-761)

-- You say that you are comparing your results to randomized trials related to effectiveness of various positions (refs 14-17). However, you have not reported on any data regarding effectiveness -- only patient satisfaction. If there are specific data that you are comparing to (e.g. patient satisfaction with the positions used in those studies), please cite that data and clearly describe the comparison.

This paragraph was modified to make it more clear as we attended only to draw a comparison on patient’s satisfaction (line 760-767).

-- "while further studies are necessary to precise the numbers" is not grammatically correct - and I am not sure exactly what you are trying to say. Increasing the numbers would allow you to statistically differentiate between narrower groups -- but it is not likely to increase the precision of your measurements. Please write this section more clearly to differentiate between actual measurements and statistical conclusions.

This was clarified in our manuscript (767-769).

Grammatical Corrections (NOTE: There are additional grammar errors that I did not note. Please have the document reviewed by a proficient writer whose first language is English to minimize errors.)

A native speaker amended grammatical error throughout the manuscript

ABSTRACT:

-- it is most common to refer to the second stage as "second stage OF labor" rather than without the preposition

-- "is similar to the McRobert maneuver" should be "is similar to the McRoberts' maneuver"

-- In "A sub-group analyses was performed according to the median of the patient satisfaction score, to assess eventual differences between more and less satisfied patients," analyses should be ANALYSIS and the comma should be deleted between "score" and "to"

All these modifications were made in the text.

INTRODUCTION:

-- "threshold largely exceeded in developed countries" should be preceded by "a" as in "a threshold largely exceded..."

-- change "approach of childbirth" to "approach to childbirth"

-- delete "in future researches." If you really want to keep it (it doesn't make sense), it should be "in future research."

-- "can be transfer to" should be "can be transferred to"

-- "could make parturient feel" should be "could make a parturient feel"

-- "resembling at the posture" should be "resembling the posture"

We modified these grammatical errors in the manuscript.

MATERIALS AND METHODS:

-- "prelabor rupture of membrane" should be "prelabor rupture of membranes"

-- "whose fetus did not engage" should be "those whose fetus ..."

-- in the discussion of the IRB approval, there should be no comma between the IRB protocol number and "and" [i.e. -00872) and declared] and there should be no period at the end of ClinicalTrials.gov

-- "would allow to appreciate the effectiveness of the intervention without being to constraining for the women" should be "would all us to appreciate ... without being too constraining ..."

-- "the primary outcomes" should be "the primary outcome"

-- if you want to include the comma in the first sentence about outcomes, then you need a subject in the second phrase (i.e. "and this was evaluated.")

-- "to evaluate participant's satisfaction" should be either "to evaluate a participant's satisfaction" or "to evaluate participants' satisfaction"

-- "A standardized question was ask to all" should be "A standardized question was asked of all"

-- "obstetrical conditions and obstetrical outcomes between women the women with higher satisfaction to the women with lower satisfaction" should be "obstetrical conditions and obstetrical outcomes between the women with higher satisfaction and the women with lower satisfaction."

-- "Data concerning risks factor of non-engagement" should be "Data concerning risk factors of non-engagement" and "peripheral nerves disorders" should be "peripheral nerve disorders"

-- "Shapiro-wilk test" should be "Shapiro-Wilk test" as it refers to a name (or pair of names)

All these modifications were made in the manuscript.

RESULTS:

-- "median weight and head circumference were respectively of 3610" should be "median weight and head circumference were respectively 3610"

-- "They are used to suggest various positions when a mechanical dystocia occurs and to help patients adopting them" should be "They are used to suggesting various positions when a mechanical dystocia occurs and to helping patients to adopt them."

We modified these grammatical errors in the manuscript.

DISCUSSION:

-- "there were no difference in participants’ " should be either "there were no differences in participants'" or "there was no difference ..."

-- "This study was not design" should be "This study was not designed"

-- "A limitation of this study consists in the absence of a reference value in the literature to differentiate between a position judged satisfactory or unsatisfactory" should be "A limitation of this study includes the absence of a reference value ..."

-- "this could inform about the efficiency" should be "this could inform about the efficacy" (or effectiveness)

-- "the role pain relief" should be "the role of pain relief" and I am not sure from the rest of that sentence exactly what you are saying, but could it be "the role of pain relief and its effect on the sense of self-empowerment."

We modified these grammatical errors in the manuscript.

Reviewer #4: Since it is stated that future biomechanical studies will be needed, the usage of computational biomechanics is already a reality, which should be recognized in the present paper, for example with the following reference

Borges, M., Moura, R., Oliveira, D., Parente, M., Mascarenhas, T., & Natal, R. (2021). Effect of the birthing position on its evolution from a biomechanical point of view. Computer Methods and Programs in Biomedicine, 200doi:10.1016/j.cmpb.2020.105921

We appreciated your suggestion and added the corresponding reference (line 878).

The description given on the text for the position used on the study is too vague. Improve the following sentence:

“Recent research in experimental settings, i.e. not during labor, suggested a particular position, similar to squatting while lying on the back (hyperflexion of the thighs and loss of the lumbar lordosis) (cf. Figure 1), could optimize delivery [3-5]”

The sentence was improved (line 129-141)

No information is given in relation to the women, in relation to their body mass index, height, weight, etc. This information is relevant.

We added the information concerning patients’ body mass, weight and height. There was no significant difference between the two groups. Result can be found in table 1 and 3.

David Desseauve

31 Aug 2021

Assessing feasibility and maternal acceptability of a biomechanically-optimized supine birth position : A pilot study

PONE-D-20-31050R1

Dear Dr. Desseauve,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.  In support of full transparency, I participated as a reviewer for the initial evaluation of this manuscript.

Within one week, you’ll receive an e-mail detailing the required amendments. When these have been addressed, you’ll receive a formal acceptance letter and your manuscript will be scheduled for publication.

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If your institution or institutions have a press office, please notify them about your upcoming paper to help maximize its impact. If they’ll be preparing press materials, please inform our press team as soon as possible -- no later than 48 hours after receiving the formal acceptance. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information, please contact onepress@plos.org.

Kind regards,

Michele J. Grimm, Ph.D

Guest Editor

PLOS ONE

Additional Editor Comments (optional):

The paper is very much improved, thank you. There are a few minor corrections that I would encourage you to make prior to final publication, listed below. Also, please make certain that the data in the tables are aligned with the correct description lines in the page proofs.

Lines 97-99 -- although you include Refs 3-5 in the prior sentence, it is not clear from reading this paragraph that the "recent research" that is discussed in those references is the same as the "in theory" work discussed previously. I would suggest that you repeat the citation of Refs 3-5 at the end of the sentence (Line 99)

Line 174 -- delete "the" before one of the authors

Line 177 -- while you have provided a direct translation from the French for the question posed to the subjects, it is very awkward in English. I suggest using one of the following:

(a) "Could you report your satisfaction about the optimized position that you were requested to use on this visual scale."

(b) "Could you report your satisfaction about the optimized position that was proposed to you on this visual scale."

Line 199 - "concerns" would more appropriately be "affects"

Line 240 - I think that you mean "low back pain related to labor THAT increased in any supine position." (capitalization used for clarity)

Table 3 - Maternal weight does not have a p-value presented, was this an oversight?

Table 3 - The obstetrical outcomes categories only have a single p-value, implying that the 3 or 4 parameters were assessed for overall difference between the groups (similar to an ANOVA). If so, make certain that the p-value is displayed in the page proofs so that it is clear that it refers to all categories of each parameter.

Line 344 - add "the" before pelvic inlet

Line 348 - As it is a new paragraph, it is not clear what "this" refers to. Do you mean "this study"? or "biomechanical analysis"

Line 356 - "fundamental" would more appropriately be "important"

Line 362 - "considered as" would more appropriately be "considered to be"

3 Sep 2021

PONE-D-20-31050R1

Assessing feasibility and maternal acceptability of a biomechanically-optimized supine birth position : A pilot study

Dear Dr. Desseauve:

I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department.

If your institution or institutions have a press office, please let them know about your upcoming paper now to help maximize its impact. If they'll be preparing press materials, please inform our press team within the next 48 hours. Your manuscript will remain under strict press embargo until 2 pm Eastern Time on the date of publication. For more information please contact onepress@plos.org.

If we can help with anything else, please email us at plosone@plos.org.

Thank you for submitting your work to PLOS ONE and supporting open access.

Kind regards,

PLOS ONE Editorial Office Staff

on behalf of

Dr. Michele J. Grimm

Guest Editor

PLOS ONE