What are women’s experiences of seeking to plan a vaginal breech birth? A systematic review and qualitative meta-synthesis

Background Guidelines for breech management at term emphasise choice and informed decision-making. Despite this, the choice of vaginal breech birth (VBB), is not always available or accessible. We aimed to describe the experiences of women seeking a VBB as reported in primary research and to offer strategies for improving this experience that are grounded in evidence. Methods We conducted a systematic review and qualitative meta-synthesis of the results, using grounded theory analysis methods (PROSPERO registration CRD42021262380), with literature published between January 2000 and February 2022. Seven databases were searched. Our review included literature about women with breech presentation, who sought a planned or unplanned VBB. Studies considering only experiences of alternative management (e.g. caesarean, external cephalic version), and those investigating healthcare workers’ experiences were excluded. Covidence systematic review software was used for screening and quality assessment. Qualitative data were extracted using NVivo software (20.5.0). Data were analysed through an iterative process based on constant comparison methods, with an iterative and reflexive code generation process. Codes were then arranged into ‘categories of experience’, which gave rise to over-arching themes. Results Our review included 19 studies. We present one overarching theory: ‘Women who wish to plan a vaginal breech birth seek connected autonomy’. Our schematic, depicting this theory, includes seven main categories of experience: paternalistic healthcare; emotional turmoil; judgement and self-doubt; mother vs society: refusing to conform; isolated but united by breech; welcomed direction; and supported self-determination and self-efficacy. Conclusions Women seeking to plan a VBB feel vulnerable and wish to connect with capable and confident healthcare providers. To meet their needs, services should be designed so that they can connect with clinicians who are willing and able to support their autonomy. Services should also seek to limit their exposure to disrespectful and judgemental interactions with healthcare providers.


Plain english summary
Members of our public involvement and engagement group and some participants in the OptiBreech research reported difficulty in attempts to access supportive care when trying to plan a vaginal breech birth.This conflicts with national guidance, which emphasises choice and informed decision-making.We wanted to understand more about the experience of seeking to plan a vaginal breech birth, so we searched for research on this topic.
We made a careful plan before we started and registered this plan.We searched seven online databases for literature published between January 2000 and February 2022.We focused on studies about women pregnant with breech babies, who sought to plan a vaginal breech birth or whose baby was discovered to be breech in labour.We used Covidence systematic review software to organise and assess the quality of the research we collected.We gathered main themes and illustrative quotes from all of the papers and compared these.We met frequently to discuss our observations and to agree on how we would summarise information we gathered.
We agreed that, overall, women who wanted to plan a vaginal breech birth felt vulnerable.They wanted to connect to confident, capable healthcare providers who could help them achieve a vaginal birth as safely as possible: 'connected autonomy.'But their actual experiences ranged widely, including: paternalistic healthcare; emotional turmoil; judgement and self-doubt; mother vs society: refusing to conform; isolated but united by breech; welcomed direction; and supported self-determination and self-efficacy.
We concluded that, to meet the needs of women who wish to plan a vaginal breech birth, services should be designed so that they can connect with clinicians who are willing and able to support their autonomy.Services should also limit their exposure to disrespectful and judgemental interactions with healthcare providers.

Introduction
Approximately 1:25 women (4%) experience pregnancy with a breech-presenting foetus at term 1 .These babies are at higher risk of a poor outcome, regardless of mode of delivery 1 .Most breech presentations are identified prior to labour, when United Kingdom (UK) and international guidelines indicate women should be offered management options to reduce this risk.These include external cephalic version (ECV) to turn the baby head-down 2 , and discussion of choices about mode of childbirth, including a caesarean birth or vaginal breech birth (VBB) with experienced professionals 1 .However, 20-30% of breech presentations remain undiagnosed until the onset of labour, in settings where universal presentation screening by ultrasound is not offered 3 .The option of turning the baby is usually not available at this point, but guidelines emphasise choice and informed decision-making about mode of birth 1,4 .
The current Royal College of Obstetricians and Gynaecologists (RCOG) guideline suggests that with skilled and experienced support, a planned VBB can be nearly as safe as cephalic birth, but throughout the UK, this level of skill and experience is frequently either unavailable or inaccessible 5,6 .Available research about women's theoretical and actual choices around mode of birth for a breech-presenting baby at term indicate as many as 35-58% of women may choose to plan a VBB when given the option, but this choice is highly dependent on the professional providing the counselling 5,7,8 .This creates disparities between what women may wish to choose and what is available for them to choose.Such inconsistencies between expectations of maternity services and its realities are likely to negatively affect women's experiences of pregnancy and childbirth.
The aim of this study was to explore the experiences of women seeking to plan a VBB, as described in primary research.We also aimed to synthesise this information into a theoretical model that could facilitate better understanding of this experience and how it might be improved.

Methods
We conducted a systematic review and qualitative meta-synthesis of the results, using grounded theory analysis methods 9,10 .With this method, we sought to generate a model that could: 1) describe women's experiences of planning a vaginal breech birth, and 2) offer strategies for improving this experience that were grounded in evidence.
Covidence systematic review software was used for screening and quality assessment.Qualitative data were extracted using NVivo software (20.5.0).Data were analysed through an iterative process based on constant comparison methods, with an iterative and reflexive code generation process.Codes were then arranged into 'categories of experience', which gave rise to over-arching themes.
The protocol was developed and registered on PROSPERO (reg.no.CRD42021262380).The review included literature about women pregnant with a breech-presenting fetus, who sought a planned or unplanned VBB, published between January 2000 and February 2022.Studies considering only experiences of alternative management, such as caesarean birth or external cephalic version, and those investigating healthcare workers' experiences were excluded.Table 1 summarises the review's Eligibility Criteria.
Seven databases were searched.The initial search was completed in July 2021; a follow-up search in February 2022 returned 1 new paper.A full Search Strategy is available in Table 2. Subject experts were contacted to identify key literature not yet published, to reduce publication bias.These sources were screened similarly to the database results.
Covidence systematic review software was used for screening and quality assessment.Two reviewers (RR and CG) carried out eligibility screening and quality assessment of the data independently, consulting a third reviewer (SW) to resolve conflicts.The results of this process are reported in Figure 1: PRISMA Flow Diagram 11 .Studies were scored to assess bias, using a points system adapted from the CASP Tool (2018) checklist, with 1 point per criteria fulfilled.Studies scoring 5 or less after a consensus was reached were excluded.Data extraction was also performed independently in Covidence, using a generated template, available in Table 3.
Qualitative data was extracted using NVIVO software (20.5.0).Data were coded independently by RR and CG, with regular meetings to discuss emerging codes.Codes were generated by constant comparison of the data and developing codes, in a reflective and iterative process, with the reviewers re-coding as necessary throughout.The data were then re-coded using the finalised codes.
Codes were organised into 'categories of experience' and relevant sub-categories, reflecting themes within those categories.This involved discussion between the review team and constant return to the data.This process is shown in Figure 2: Concept Map.The lay member of the team, who also had access to the primary sources, checked the resonance of our emerging findings and highlighted key areas needing further analysis.A grounded theory was developed to explain the way in which the identified categories and themes interacted.

Results
Our search returned 1395 studies once duplicates were removed.
One study was discussed by all 3 reviewers after scoring 5 at quality assessment; the decision was made to include the study due to its value in exploring breech birth decision-making.Studies included qualitative (14), mixed (4) and systematic review (1) methods.Nine countries and international on-line samples were represented.Lead authors included midwives (8), service users (6) and obstetricians (5).Characteristics of included studies are summarised in Table 4.
We approached our meta-synthesis using the constant comparative methods of grounded theory 10,12 .Our initial analysis generated 94 codes, from which we developed categories and subcategories classified by types of experiences.These included seven main categories: paternalistic healthcare; emotional turmoil; judgement and self-doubt; mother vs society: refusing to conform; isolated but united by breech; welcomed direction; and supported self-determination and self-efficacy.
Considering the sum of the data, we developed an overarching theory: Women who wish to plan a vaginal breech birth seek connected autonomy.We organised the categorical experiences of seeking to plan a VBB on a schematic axis, reflecting how women's feelings of connection and support intersected with their ability to exercise personal autonomy.This is represented in Figure 3: Connected Autonomy Schematic.

Paternalistic healthcare
In the 'isolated constraint' quadrant of our schematic, women's experiences were characterised by disconnection from their healthcare providers and little ability to make autonomous decisions about mode of birth.
In many instances, women were denied the choice of a VBB: "There was a void between the information they received and the information they wanted.p4) Where the option was mentioned, it was accompanied by highly emotive and frightening descriptions of breech births that had gone wrong: "You don't have a choice, your babies are going to die, you are going to die, why did you come here if you don't want us to help you, your kids will be left without a mother …" 14(p43) It was a priority for most women that they "retained control of decision-making, retained a sense of personal choice and retained the option of having a vaginal birth," 15(p10) but this did not happen in many cases.pe212) This created disconnect between women seeking a VBB and their providers.Some women perceived the support from encouraging healthcare professionals to be curtailed by their colleagues, which undermined their trust in the healthcare team.
Women expected providers to have adequate training to support  VBB but found this was often not the case: "I feel it's a shame there is not more education and support for new doctors coming through.p45) This highlights the imbalanced power dynamic between mothers and healthcare professionals, and amongst professionals themselves, that enforces paternalistic care.
Even in settings where VBBs were more common, some of this lack of control persisted.Women planning a vaginal birth reported lack of involvement in decision-making more often (29.6%versus 2.9%) 17 and fewer felt the final decision on mode of delivery was theirs rather than the doctor's (60% versus 85%) 18 , compared to women planning a caesarean birth.Toivanen et al reported the only significant difference between the experience of women attempting breech and vertex births was a significantly reduced sense of participation in their birth 19 .

Emotional turmoil
Experiences of 'isolated constraint' also led to significant 'emotional turmoil.' Women felt strong negative emotions when receiving their breech diagnosis, including fear and anxiety 14,16,[18][19][20][21][22] , uncertainty 16,[23][24][25] , powerlessness 23,25 and grief: "I don't talk about it I guess but when I do I get quite upset.p131) Their emotional turmoil was exacerbated when women were not given an opportunity to express their feelings and wishes 23 .
Women's emotions surrounding breech were influenced by their own experiences, and those of people around them.Family pregnancy and childbirth experiences were especially important, with unresolved trauma from previous experiences generally influencing mothers to opt for planned caesarean birth.
Women also felt that breech diagnosis was 'a time-sensitive issue'.Transitioning from passive to autonomous decision-making required information, which took time to receive or seek out.The timing of breech diagnosis often played a role in mothers' reactions and decisions.p3127) Many women felt they missed the chance to be better prepared, and most studies found that women preferred earlier diagnosis of breech presentation 24 .

Judgement and self-doubt
Most women who actively tried to plan a VBB experienced 'judgement and self-doubt,' an experience of 'lonely autonomy.'Women reported frustration that they were considered "not capable of making the right decision" 15(p9) about their birth and feeling devalued as part of their own healthcare.Enhanced communication was an important and recurrent suggestion for improvement, as women often felt their motivations for a VBB were misunderstood.
In addition to healthcare professionals, "pressure and judgement from family members" 14(p43) also influenced the decision-making process 16,[20][21][22][24][25][26][27][28] . Many flt "upset when family and friends accused them of being selfish and 'putting the birth before the baby.'"15(p8) "People in women's social networks related to the women that breech presentation posed life-threatening risks for mother and baby."22(p1394) Avoiding the self-doubt this engendered required women to distance themselves from others: "I switched off to it because I was confident with my decision."15(p7) One woman shared how she withheld information  about her birth plans from friends and how she "disengaged from the 'ones that doubted.'"25(p141) Women felt alone in assuming responsibility for their decision: "It's a decision where you are fundamentally alone at the end.
Even if there are people who are there with you, you're finally the only one to have to assume such a decision.pe212) Where they ultimately chose to plan a caesarean birth, often women still felt misunderstood and alone with their grief.One woman explained "And the fact that I thought I was going to miss out on that part, I was already grieving it.p4) Mother vs society: refusing to conform This category was also characterised by 'lonely autonomy'.
Women with plans for a VBB encountered resistance and barriers at all levels: social circles, clinicians, and institutional policies: "To try for a natural breech birth and go against the status quo -that's a really hard thing to do." 15(p10) Many possessed strong self-determination and self-efficacy at odds with systems that failed to accommodate this.Many women felt they were 'fighting' the people and systems who were supposed to be caring for them.
In "'going against the tide' of current practice," 15(p23) most women also had to "circumvent a system that was blocking them from attempting a VBB." 13(p5) Where local providers were inexperienced or unwilling, choosing not to have an elective caesarean birth meant women had to transfer hospitals to access a VBB.p3129) Some women were forced to travel long distances [13][14][15]22,[24][25][26]28 , introducing a physical disconnect between them and their primary providers.
After overcoming these challenges, women often encountered additional institutional barriers, such as policies preventing experienced providers from caring for them, at all or outside of regularly scheduled working hours.Although balanced information made a significant difference to women's decision-making 7,29 , many women encountered systemic barriers to accessing balanced, evidence-based information 21 .
Isolated but united by breech Some women found support in social media networks.These served as an "alternative support system" 15(p13) to women experiencing judgement and isolation from their usual social networks after deciding to pursue VBB.Women accessed social media during their information seeking activities, finding it helpful to "read birth stories and get good support online from breech moms across the globe" 14(p44) which in turn, often helped to alleviate anxiety 23 .For many, participation in these networks was influential in their decision-making process, with the effects of social media ranging from "an additional support" 20(p119) to "hugely helpful and motivating when making [their] decision" 14(p44) .They used these forums to counter the isolation they were experiencing and seek validation and assurance.

Supported self-determination and self-efficacy
A small minority of women had experiences of planning a VBB that were characterised by 'supported self-determination and self-efficacy,' an experience of 'connected autonomy'.
These women received care that aligned with their expectations of how services should operate: "My appointment with the specialist went so well today!… It's all systems go for an active breech birth!Woohoo!He didn't even question my decision.pe99) Multiple papers described how women sought out clinicians, described as 'specialist[s]' 14,20,[24][25][26][27]30 , who presented them with unbiased information and encouraged them to be an active part of decision-making, even if this meant changing providers. Fiding this person significantly alleviated many women's anxieties and boosted their personal feelings of self-efficacy in decision-making and birth.Women also highlighted continuity of carer as an important factor in building a trusting relationship.Midwives were often seen as 'allies', with the ability to navigate the healthcare system to meet mothers' needs.
Women who attempted a VBB experienced a range of emotions, very similar to their counterparts who experienced cephalic birth 19 .Some who achieved a planned VBB felt proud of their birth experience and recalled the importance of being 'fully-engaged' 25(p141) in the birthing process.In many cases, the eventual outcome of the birth route was less important than having the choice and opportunity to try for a VBB, of 'having a go' 13 .
Multiple studies concluded that "experience of healthcare professionals is also a key characteristic that is perceived to increase the likelihood of a more positive experience and a more favourable outcome to [a] breech birth" 23(p77) .p3126) Welcomed direction While most women sought active decision-making roles about their care, some preferred to defer to their care provider, welcoming their direction.This experience fell in the 'supported direction' quadrant of our schematic.Some women preferred not to share decision-making; they preferred clear advice from professionals: "It was their decision not mine which was fine.p151) This preference appeared to apply to both caesarean and vaginal birth: "…I'll be scheduled for a c-section on Wednesday.Personally I wouldn't deliver him vaginally … my hospital don't even consider vaginal breech delivery!So I couldn't have one if I wanted to." 27(pe99) Although most women expressed a preference for earlier, antenatal diagnosis of breech presentation 23 , a small minority preferred their late diagnosis.These were mostly women whose baby's breech presentation was diagnosed during a labour that ended in a healthy vaginal birth.This is because they knew less of the potential complications, which they perceived would have negatively impacted their experience.p1395) We placed this category in a lower quadrant due to the lack of autonomy exercised by women in decision-making.The women themselves chose to pass this responsibility to their care providers which is distinguished from the experience of 'paternalistic healthcare,' where women experienced their right to choose as withheld.

Main findings
Our study highlights the need for women to experience 'connected autonomy' and 'supported direction' during breech pregnancy and childbirth.Most women prefer autonomy over their mode of delivery and want non-judgemental support from skilled healthcare professionals regardless of their choice of birth mode.Most women value discussing their priorities with their healthcare providers and receiving balanced advice, i.e., supported direction.
Unfortunately, our review found that many women experience lonely autonomy and isolated constraint.In fighting for their birth choices many women found themselves alone and unsupported.Complying with the advice of their healthcare professionals, when in direct conflict with their preferences, led to feelings of regret and dissatisfaction.
Despite guidelines recommending that women be offered a choice regarding their delivery, our research indicates that many women found the choice of VBB is neither offered nor available.Even when willing and/or skilled birth attendants are available, systems are not set up to facilitate this.As a result, many women feel disconnected from their healthcare providers when they are most in need.

Strengths
This study benefits from careful consideration of bias throughout the research process.All screening, bias assessment, and data extraction were performed by both reviewers independently before discussion to reach a consensus, to prevent selection and interpretation bias.The two primary reviewers were medical students, and the senior supervising member of the review team was a midwife.Inclusion of studies recruiting social media or blog posts prevented sampling bias and reduced the effect of primary researchers on participants.Experts were consulted to identify key literature not retrieved by the literature search (for example, grey literature) to reduce publication bias.
Throughout the data coding and theme developing process, a service user was consulted to check resonance of the emerging findings.This further reduced interpretation bias and increased the transferability of our findings.They also helped to ensure our results were presented with balance and accuracy, in a way likely to be acceptable to women in our population of interest.

Limitations
The strict eligibility criteria of the study may have reduced the scope of our review, and the search of databases for literature may not have retrieved all relevant results.The findings of this study may be less applicable to healthcare contexts that differ from those included in the study, as the nature of women's experiences of VBB is both deeply personal and highly dependent on the services accessible.Only English language studies were included.

Interpretation
Our study included literature from a wide variety of settings, including some settings that have frequent VBB.In settings where VBB was less common, conflict with healthcare providers appeared more frequent.While our study focused on the experience of planning a VBB, evidence from the included studies indicated that women's dissatisfaction arose from lack of support for their preferred mode of birth and ability to make autonomous, informed decisions.Multiple studies have reported high levels of satisfaction when women's request for a planned caesarean section is fulfilled, despite higher levels of postpartum complications when there is no medical indication 18,31 .
In the few studies completed in settings where VBBs were common, feelings of lack of control and involvement in decision-making were still more common when compared to women planning vertex or caesarean births.This may be because of the historical focus on 'selection criteria' for selecting women who are 'good' candidates for VBBs.Such criteria often fail to align with women's own feelings about their birth choices, which should be at the core of person-centred healthcare.
We hope that this review will help healthcare providers to understand the experiences of women who seek to plan a VBB at term.Although this choice is often viewed in opposition to the 'mainstream', in which most women are advised to and choose to plan a caesarean birth for their term breech baby, a significant number of women only reluctantly choose this position.Women who wish to plan a VBB also want to work in partnership with supportive, skilled providers.Services can and should do more to ensure they are able to do this.

Implications for future practice, policy and research
Our findings suggest that specialist services dedicated to breech births would be beneficial for mothers.There have already been previous calls for such services 24,32 , and currently some integrated care pathways are in development 33,34

Conclusions
Our review aimed to explore women's experiences of planning a VBB.Our findings show that women seek connected autonomy and supported direction yet often encounter lonely autonomy and isolated constraint.While there is a demand for VBB, women frequently feel pressured to accept the more mainstream option of caesarean birth and struggle to access supportive services.We found that women felt misunderstood in their motivations behind seeking VBB and felt alienated from a society labelling them 'selfish'.Women felt communication with clinicians was vital to their birth experience and turned to their peers for support and to seek shared experiences.
Ensuring women have 'connected autonomy' is vital to improving the breech birth experience.Women are vulnerable during this time and seek capable and supportive clinicians to help them achieve the birth they desire.Our recommendations include dedicated breech specialist pathways, increased availability of balanced, reliable educational resources for mothers, and improvement of training for clinicians to ensure wider access to experts in breech presentation and VBB.Further research will be needed to explore the clinical and cost effectiveness of these potential solutions.

Ethical approval
As this was a systematic review and did not concern any primary or non-anonymised data, no ethical approval was sought.

Megan Cooper
Flinders University, Adelaide, South Australia, Australia Thank you for the opportunity to review this manuscript which examines the experiences of women who seek a vaginal breech birth.This is a much needed examination that has significant implications for care across the globe, especially with respect to women's autonomy.
The paper is a pleasure to read and is extremely well written.This is a credit to the authors.Minor recommendations and suggestions are provided below.
Within the plain English summary there is reference to the categories but they are not referred to as such.I would suggest that you refer to the findings as categories as you have throughout the paper to avoid any confusion.
In the first paragraph in the introduction, there is reference to women being offered management options to "reduce the risk."Do you mean the risk of breech presentation or the risks associated with experiencing a breech birth?
Can you explain the rationale for the inclusion criteria from January 2000 and February 2022?Following the Term Breech Trial, much changed.Was this the reason?I would suggest that it would be worthwhile to provide the rationale.
"Constant return to the data" on page 6 reads a little clumsy.I am also wondering whether "interacted" is the right word when referring to relationship between categories and themes?
While a very different focus, I can draw very strong similarities between these findings and the barriers and challenges that women experience in accessing water immersion for labour and birth and other options that are not mainstream or well-accepted.Is there scope for these similarities to be drawn to emphasise that the issue transcends vaginal breech birth and is reflective of the state of maternity services more broadly?That is, women's autonomy is only supported where their decisions align with what the individual practitioner, institution and/or policy support.
Page 9, second paragraph under "Emotional turmoil" -are you referring to unresolved trauma relating to family experience of breech birth or birth more generally?
Given the generalised lack of support for vaginal breech birth, is it more important that there is greater education to overcome the negativity rather than services that are specific to breech?There is clearly an aversion and while the premise of specialised breech clinics/services may address the issue of women's access to a supportive clinician, it is unlikely to change the broader and arguably, entrenched view, that vaginal breech birth is unsafe.Can you provide suggestions for how this somewhat systemic view of breech birth might be challenged?
Are the rationale for, and objectives of, the Systematic Review clearly stated?Yes

Are sufficient details of the methods and analysis provided to allow replication by others? Yes
Is the statistical analysis and its interpretation appropriate?Not applicable

Are the conclusions drawn adequately supported by the results presented in the review? Yes
Competing Interests: No competing interests were disclosed.
Reviewer Expertise: Midwifery, maternity care, women's experiences of maternity care, informed decision making I confirm that I have read this submission and believe that I have an appropriate level of expertise to confirm that it is of an acceptable scientific standard.

Methods:
Can the authors explain why they chose such a wide interval for their studies?January 2000 was before the publication of the Term Breech Trial, but no doubt many other things in the management of breech position have changed in the intervening years. 1.
Figure 2, the concept map, shows the themes found, and therefore belongs in the results section.

2.
I am missing a description of the background of the authors/researchers.In qualitative studies, the eyes looking at the data are never neutral, that would be impossible.So it would help to know the positions of the authors and the level of their involvement in breech care. 3.

Results:
Very well written, interesting quotes and easy to glean the larger picture.1.
Figure 3 is interesting and novel!Has this been done before?Do you have a reference for this? 2.

Discussion:
I am missing a wider scope for this issue.Women encounter physicians who are inexperienced and/or afraid.The causes of this would be interesting.The Term Breech Trial, the reduced experiences for trainees, the increase in audits and legal ramifications… 1.
A parallel could be drawn with the literature on birth choices against medical advice.Those women also encounter a lack of autonomy, and report more satisfaction when they have felt heard, regardless of how the actual birth went.

2.
Some comment could be made on the different setting and approaches to breech birth, especially in light of the tone on international breech platforms on social media.In many countries, VBB is a regular option, even if not exactly welcomed by all providers.However, in the US, this is mostly not the case.This has led to a whole subculture of service users (or rather, refusers) on the internet who seem to want to convince all women with a breech presentation that it is no different than vertex, and that a home birth is safe.

3.
Do the authors have any concrete suggestions for dedicated services?And about how they would impact unexpected breech births and twins births?

4.
Are the rationale for, and objectives of, the Systematic Review clearly stated?Yes

Are sufficient details of the methods and analysis provided to allow replication by others? Yes
Is the statistical analysis and its interpretation appropriate?

Not applicable
Are the conclusions drawn adequately supported by the results presented in the review?

Table 1 .
Eligibility criteria.Only studies that satisfied every element of the inclusion criteria were included.Studies were excluded if they fulfilled any 1 or more of the exclusion criteria.
RCT's, case-series, discussions, lettersContextStudy published in or after the year 2000, about human subjects, in EnglishStudies published prior to the year 2000 Table 2. Search Strategy.Search terms were formulated by identifying key words covering the criteria of PEO: Population (women), Exposure (vaginal breech birth) and Outcome (experience).Synonyms and variations of key words were then generated.Search terms were refined by running scoping searches.