Approaches to improving the contribution of the nursing and midwifery workforce to increasing universal access to primary health care for vulnerable populations: a systematic review

Background Despite considerable evidence showing the importance of the nursing and midwifery workforce, there are no systematic reviews outlining how these cadres are best supported to provide universal access and reduce health care disparities at the primary health care (PHC) level. This review aims to identify nursing and midwifery policy, staffing, education and training interventions, collaborative efforts and strategies that have improved the quantity, quality and relevance of the nursing and midwifery workforce leading to health improvements for vulnerable populations. Methods We undertook a structured search of bibliographic databases for peer-reviewed research literature using a focused review question and inclusion/exclusion criteria. The quality of retrieved papers was appraised using standard tools. The characteristics of screened papers were described, and a deductive qualitative content analysis methodology was applied to analyse the interventions and findings of included studies using a conceptual framework. Results Thirty-six papers were included in the review, the majority (25) from high-income countries and nursing settings (32). Eleven papers defined leadership and governance approaches that had impacted upon the health outcomes of disadvantaged groups including policies at the national and state level that had led to an increased supply and coverage of nursing and midwifery staff and scope of practice. Twenty-seven papers outlined human resource management strategies to support the expansion of nurse’s and midwives’ roles that often involved task shifting and task sharing. These included approaches to managing staffing supply, distribution and skills mix; workloads; supervision; performance management; and remuneration, financial incentives and staffing costs. Education and training activities were described in 14 papers to assist nurses and midwives to perform new or expanded roles and prepare nurses for inclusive practice. This review identified collaboration between nurses and midwives and other health providers and organizations, across sectors, and with communities and individuals that resulted in improved health care and outcomes. Conclusions The findings of this review confirm the importance of a conceptual framework for understanding and planning leadership and governance approaches, management strategies and collaboration and education and training efforts to scale up and support nurses and midwives in existing or expanded roles to improve access to PHC for vulnerable populations.


Background
Universal access is an important step towards universal health coverage to ensure that all people receive the health services they need without suffering financial hardship [1]. Evidence suggests that the provision of affordable, acceptable, high-quality health services [2] leads to better access to necessary care and improved population health, particularly for growing numbers of vulnerable individuals and communities [3] who experience significant health disparities [4]. However, achieving universal access to reduce health inequity and realize improved health outcomes requires competent and motivated nurses and midwives [5] who form the largest group of the world's health workforce.
The coverage of nurses and midwives, in terms of adequate numbers and their appropriate distribution in locations where the community can access them, is critical [6]. A direct association has been observed between health worker density and maternal, infant and child survival. In particular, the density of nurses has been found to have a significant independent effect on maternal mortality which has not been demonstrated for doctors [7]. Recent calculations also show that scaling up midwifery-delivered interventions from present baseline levels in 78 countries could significantly reduce maternal deaths, stillbirths and neonatal deaths [8].
These findings reveal the importance of accessible nursing and midwifery-led health care within the community at the primary health care level [9,10]. Nurses and midwives can play a key role in empowering patients and strengthening community involvement in their health [11] through knowing and understanding the health needs of local populations and targeting interventions to meet the wider determinants of health [12]. The education and training, as well as the socio-culturally diverse composition of the nursing and midwifery workforce, may facilitate the appropriate delivery of relevant health care [13,14] and promote health equity among distinct populations [15,16].
In addition to adequate numbers of competent nurses and midwives whose backgrounds reflect the diversity of the population they serve, effective human resources for health leadership and management is also an important consideration in the delivery of accessible health care. Well-regulated nursing staff with the appropriate workloads and skills mix has been associated with improved patient satisfaction and health outcomes [17,18], while inadequate nurse staffing levels have been associated with an increase in adverse events and poor care [19]. However, nurses and midwives cannot deliver care on their own, and in order to achieve universal access and health equity, partnership and collaboration are necessary at the policy level [20] and in practice [21].
Despite considerable evidence showing the importance of the nursing and midwifery workforce, there are no systematic reviews outlining the contribution that these cadres have made to achieving universal access and reducing health care disparities at the primary health care level. Research gaps have been noted in this broad area [4]. Insight into how nurses and midwives can be best placed and supported to deliver care to address the health needs of vulnerable groups at the primary health care (PHC) level, or the first level of contact, should inform the decisions of policy makers with respect to realizing efficient workforce and service planning to achieve health equity. This paper aims to identify nursing and midwifery policy, staffing, education and training interventions and collaborative efforts and strategies that have been found to improve the quantity, quality and relevance of the nursing and midwifery workforce that have ultimately led to health improvements. In particular, the review sought to identify nursing and midwifery workforce interventions and approaches that have led to: An increase in the number of well-trained, motivated nurses and midwives to provide the services to meet patients' needs based on the best available evidence The provision of greater access to nursing and midwifery health services, care, information and essential medicines and technologies to diagnose and treat medical problems and A reduction in the cost of care making nursing and midwifery health services more affordable to those suffering financial hardship A framework for understanding the factors contributing to universal access A framework was developed to conceptualize the various elements under investigation and the relationships between them (see Fig. 1). This framework is based upon the approach outlined in a discussion paper prepared for the 2014 WHO Global Forum for Government Chief Nursing and Midwifery Officers [22]. The framework helps to describe the link between nursing and midwifery leadership and governance, workforce strengthening interventions, nursing and midwifery practice and universal access and health equity. The link between leadership and governance on action and intervention is drawn from evidence of the impact of leadership upon patient outcomes [23] and acknowledges the importance of leadership at the management level [24] and the practice level in service delivery [25,26]. Nursing and midwifery workforce areas are based upon human resources for health (HRH) performance fields that can describe both interventions and indicators to support and assess HRH performance [27].

Methods
Eight bibliographic databases, Google Scholar and the reference lists of key papers were systematically searched to retrieve research literature. A deductive qualitative content analysis methodology was applied to analyse selected research papers [28].
A Population, Interventions, Comparators, Outcomes, Study (PICOS) question design was used to guide the development of the review question [29]. The review question was for vulnerable populations: What nursing and midwifery governance and workforce interventions have increased access to quality health care at the primary health care level? The review aimed to source studies of nursing and midwifery interventions designed to increase access to health care with demonstrable outcomes for access and health equity. We sought to identify efforts to increase the supply of nurses and midwives, expand their roles and improve their regulation, performance management and remuneration, as well as opportunities for education and training and collaboration. Outcomes of interest included the following: Fig. 1 A conceptual framework for examining nursing and midwifery leadership and workforce interventions and their impact on universal health access improved availability of health services and accessibility, acceptability and quality of health care and enhanced health outcomes. Observational studies and quasiexperimental and non-experimental descriptive studies were considered suitable for inclusion, and a systematic search of the contemporaneous primary research literature published from 2005 to 2015 was undertaken. Electronic databases and the internet were searched using the keywords "nurs*" OR "nurse-led" OR "midwife*" OR "midwife-led" AND "leadership" OR "workforce" OR "staffing" AND "universal health coverage" OR "equity" OR "access". The Medical Subject Headings (MeSH) headings "manpower" and "Nursing" and "Midwifery" and "Nurse Midwives" were also used and augmented by the keywords "equity" and "access".
In this review, we adopted the World Health Organization's (WHO) definition of primary health care (PHC) as the first level of contact that individuals, the family and the community have with the national health system, which constitutes the first element of a continuing health care process [30]. For the purpose of this paper, we defined a vulnerable population as a subgroup or subpopulation who, because of shared social characteristics, is at a higher risk of factors such as unsafe sex, stress, drug misuse and malnutrition that can impact upon health issues including HIV and diabetes as well as access to health care [31]. Examples of vulnerable populations include refugees, the elderly, the homeless, the poor, ethnic minorities, incarcerated people, children, those living in rural and remote settings, families experiencing domestic violence and adolescent mothers. Such groups may have multiple vulnerabilities and health risks.
Retrieved records were first screened for their focus as per the review question by the first author and duplicates removed. As per the inclusion/exclusion criteria (see Table 1), discursive papers, those older than 10 years or whose focus was outside of the aim were removed. The Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines were used to report the review process [32] (see Fig. 2). The sources and numbers of papers retrieved and screened according to their relevance are outlined at Table 2. Seventy-five papers were then excluded at closer inspection as they were not concerned with interventions at the PHC level or focused on addressing the needs of vulnerable populations, nursing and/or midwifery workforce interventions were not described or they were discursive papers. Forty papers were appraised using the Critical Appraisal Skills Programme (CASP) tool for qualitative research [33], and Pluye et al.'s [34] scoring system was used to assess the non-experimental and mixed method studies. Four items were discarded due to methodological concerns [35][36][37][38].
Data were extracted from the 36 papers and first described according to general study characteristics (e.g. primary author, year of publication, context of the study), participants (age, gender and sociodemographic data), study aim, study design and findings (see Table 3). The conceptual framework outlined in Fig. 1 was then applied to identify the workforce, leadership and governance strategies described in the studies that had impacted on universal health access for vulnerable populations. A content analysis of the extracted text relating to each identified workforce, leadership and governance strategy was performed. This involved coding text according to emergent descriptions and then labelling and grouping them according to key HRH performance areas relating to policy, management, collaboration and education and training. Tables and concept maps were used to plot patterns and relationships across the categories and robustness assessed through critical reflection and discussion among the three authors.

Results
Thirty-six papers were included in the review. Eleven papers described research in low-and middle-income country (LMIC) contexts (Uganda, South Africa, Indonesia, Kenya, Cameroon, Rwanda and Tanzania) [39][40][41][42][43][44][45][46][47][48][49] and 25 from high-income contexts (HIC) (Germany, the United Kingdom, the United States, Canada, Australia, The Netherlands, New Zealand) . Four papers were concerned with outcomes related to midwife-led interventions (antenatal, intrapartum and postnatal care and prevention of child abuse) [41,50,57,58], while 32 focus on nursing, some on specific health issues including asthma [62], eczema [54,69], cardiovascular disease [44], diabetes care [42,45,51,66,72], HIV/AIDS [39,47,48], mental health [40,61,65] and women's health [46]. Different types of nurses were described providing care at the first point of contact in the various studies. These      Six themes emerged from the focus group data that illustrated key issues for the implementation of the CHT: "agreeing the focus", "strong leadership", "the challenge of communication", "managing workloads and new ways of working", "success of the CHT" and "outside influences". Communication and heavy workloads were identified as key barriers to the success of the CHT in the questionnaire data.  Retention rates in groups 2 and 3 were 60% and 65%, respectively, against 29% in the control group. The differences between the intervention groups and the control group were significant (P < 0.001), but differences between the two intervention groups were not (P = 0.719). There were no significant differences in BP or fasting plasma glucose trends between retained patients in the study groups. Average monthly cost to patients for antihypertensive medication was €1.1 ± 0.9 and for diabetics €1. Qualitative in-depth, face-to-face interviews using interpretive description methodology 9 rural women, aged 18-80 using nurse practitioner services To explore rural women's experiences with primary health care nurse practitioners The participants in the study particularly appreciated the nursing knowledge of the NP, the time the NPs spent with them, and the thoroughness of the care provided by NPs. These foundational elements of the participants' experiences with rural NPs created a sense of trust and respect, which lead to a collaborative partnership between the NP and the rural women. The majority were over 40 years of age, were female, were single, completed high school and were poor and uninsured, and many were unemployed. The most frequent health problems were related to pain, cardiovascular symptoms, dentition problems and respiratory illnesses. The most frequent nursing interventions were for    nurses included the following: nurse practitioners [63,68,70] and advanced nurse practitioners [52,65,67], certified nurse specialist [51], psychiatric nurses [40], paediatric nurses [52] intermediate care nurses [53], community nurses [64,65] community-based nurses [54,55], community staff nurses [44,55], district nurse [55], specialist dermatology nurses [54] or practice nurses working with general practice (GP) doctors [54,62,69], diabetes specialist nurses [42,66], diabetes nurses [42,72], local diabetes trained nurse [45], women's health nurses [56], public sector nurses [43], registered nurses [43,44,59,64,65,67,73], registered nurses working in a community nursing agency [64], registered nurses working in a public health agency [64], nurse managers [59], respiratory nurse educators [62], nurse care managers [65], mental health nurses [65], PHC nurses [42,45,46], child health nurses [69], auxiliary nurses [40], enrolled nurses [40,43], nurse assistants [44], general nurses [40], primary care nurses [60], school nurses, [60], public health nurse facilitators [60], head nurses [44], antiretroviral (ARV) nurses [48], student nurses [74]. Specific vulnerable populations formed the focus of many papers including children [48,50], the elderly [55,61,64,65], ethnic minorities [40,51,57,72], indigenous people [58,67], the homeless [53], the poor [39,41,44,52,54,56,60,68,69,73], prisoners [59,66], those living in rural locations [42, 43, 45-47, 49, 62, 63, 70] and people with substance use disorders [71]. Some populations had multiple vulnerabilities such as families described in the Ayerle et al. paper [50]. Most studies were quantitative [39-47, 49, 51-53, 56, 61, 62, 64, 66-70, 72-74], followed by mixed methods [48,50,54,57,58,60,65] and qualitative [59,63,71] research. Most studies were intervention studies where a new or existing nurse or midwife-led initiative was evaluated, while other research examined the effect of a service where the nurse or midwife had played an important role. Other studies analysed in this review involved the secondary analysis of data to examine the impact of nursing or midwifery care over time [41,43,52]. One study focused on an education intervention to prepare student nurses to care for vulnerable populations [74] Table 4 outlines the focus of policy, governance and workforce strategies and approaches described in the studies as part of outlined interventions to improve the supply or support of midwives and nurses to deliver care to enhance the health outcomes of vulnerable groups. Twenty-seven of the 36 papers contained some mention of human resource management (HRM) strategies and approaches, while 22 papers described collaboration, 14 education and training efforts and 11 leadership and governance approaches. Only three papers contained descriptions of policy, HRM strategies, collaboration and education and training efforts [41,48,59]. The content analysis of the papers provided further detail and insight into how such strategies and approaches had been utilized to improve access to the care delivered by nurses and midwives. These findings are outlined below according to the key areas.

Leadership and governance
The analysis of 11 papers identified policies at the national and state level that had impacted upon the increased supply and coverage of nursing and midwifery staff and scope of practice. Two papers describe the Indonesian and Kenyan government's efforts to increase the numbers of midwives and nurses through scaling up education and training and deployment to underserved areas, particularly poor rural communities. In Indonesia, the presence of village midwives led to significant increases in women's acceptance of iron tablets and use of antenatal care during the first trimester of pregnancy [41]. In Kenya, the Emergency Hiring Plan (EHP) increased the number of nurses in remotes areas by 37% and enabled the number of functioning public health facilities to increase by 29% [43]. Two papers from Rwanda [47,48] describe the Ministry of Health's collaboration with international donors to develop models of task shifting, or the delegation of specific HIV/AIDS tasks in a context of chronic workforce shortages, to optimize nurse performance to deliver care to adults and children with HIV/AIDS. The government's commitment also included the provision of additional nursing staff supported by laboratory staff and ongoing laboratory services, training and antiretroviral procurement [48].
Other policy and regulation efforts to expand nurses' scope of practice to better deliver care to vulnerable populations are described in two papers with respect to nurse practitioners (NPs) and advance nurse practitioners (ANPs). Leipert et al. [63] refer to the Canadian Nurses Association and Government-supported initiative to better integrate NPs into health care while a study by Oliver and others demonstrates that American States with legislation allowing full practice of nurse practitioners have lower hospitalization rates among Medicare-Medicaid beneficiaries and improved health outcomes in their communities [68]. Research by Sears et al. also found that the implementation of the Washington State workers' compensation system, which involved the expansion of the NP scope of practice to increase access to health care for injured workers in rural areas, resulted in increased NP participation and a 16-percentage-point improvement in timely accident report filing by NPs particularly in rural areas [70].
Government support for the introduction and expansion of nurse-led clinics through policy and funding investment was reported in a New Zealand study whose examination of consultations over an 18-month period demonstrated a significant (>30%) reduction in child eczema severity, fewer child hospitalisations and a 50% reduction in family antibiotic use among Maori/Pacific Island and other low socio-economic groups [69]. A review of patient records at one of the first urban academic-nurse-managed clinics in America reported a range of interventions delivered to 334 urban Native Americans [67]. This nurse-led care, according to a previous study of this service, was valued by Native Americans particularly the advocacy that nurses provided on behalf of clients and the continuity of care [75].
Other papers provide examples of nursing leadership in practice. Leadership was reported to underpin successful collaboration between police and nurses in a local government region in Scotland that allowed nurses to focus on the delivery of quality care for prisoners [75]. "Strong leadership" from the Public Health Nurse Facilitator was regarded as critical to the functionality of the community health team in England to provide mainly nursing care to deprived areas [60].

Nursing and midwifery management
Descriptions of the roles of nurses and midwives featured in the reviewed papers, followed by issues of staffing supply, distribution and skills mix; workload; supervision; performance management; and remuneration, financial incentives and staffing costs. A wide range of primary health care nursing and midwifery roles was described in the papers that contributed to improved outcomes for vulnerable populations. These included taking patient histories, screening of new patients, the surveillance of physical signs and symptoms, conducting diagnostic tests and screening for side effects, cleaning wounds, infection control, prescribing and provision of medication, assessment of social issues, education and counselling of patients, establishing contracts with patients to manage health issues, completing and submitting official forms and reports, referral and community health promotion and advocacy. Nurses and midwives worked in clinics and provided outreach services and home visiting. NP roles were described as autonomous [63] and licensed as independent health care providers whose roles were similar to those of primary care physicians [70] and who consulted with doctors as needed [63]. However, one study noted that where NPs required a doctor's signature to process compensation for injured workers, delays in health care and accident report filing were observed, particularly for rural or underserved populations [70]. Role challenges and issues were noted in two studies. Proscribed and narrowly defined nursing roles in two studies presented by Goodman et al. were said to result in nurses limiting their involvement in district nursing efforts which led to nurses feeling ambivalent about their roles [55]. Concerns were raised in a research by Dorney-Smith about role isolation and conflict that nurses may experience while working in a hostel for homeless people which may lead to "burn out". A number of suggestions were offered to deal with such issues if they occurred, including the presence of management at a weekly handover meeting to provide supervision and support, monthly one-to-one and group supervision and rotations to enable time away from the hostel at the main team office [53].
Many of the studies outlined the role that nurses and midwives played in the delivery of new interventions which involved the addition or specialization of the tasks they performed. This was described as an expanded or extended role using delegation or task shifting. The design and implementation of community-based health promotion, education and advocacy were regarded as expanding the role of Women's Health Nurses in a paper outlining a programme focused on building resilience and social capital through networks in a disadvantaged community in urban Australia [56]. The addition of the provision of care to injured workers as part of newly introduced compensation legislation was also described as expanding the role of NPs [70]. The roles of two diabetes nurses who set up a weekly diabetes clinic in a rural area of South Africa were seen to have taken on extended nursing roles while diabetes-related tasks were delegated to other nurses who showed interest in the clinic in order to optimize the service [45]. Shifting specific tasks to nurses, in addition to their usual work, to scale up the care of poor rural dwelling Africans with HIV/AIDS, hypertension and diabetes was the focus of research outlined in two papers [44,47]. Supportive mechanisms were developed to assist these nurses in their role, including the modification of clinical data collection forms, checklists and job aides to guide the process of data collection [47] and clear processes for setting up contracts with patients for disease management [44]. Shifting tasks to nurses through nurse-led clinics was found to have positively impacted upon doctors' workload [69].
Strategies to optimize nurse's performance and ensure appropriate workloads through task shifting from nurses to other health workers were described in two papers included in the review. Health support workers were employed in a homeless hostel, and tasks associated with dressings, observations, and medications that would normally have been undertaken by nurses shifted to this cadre so that the caseload for the nurse could be increased to best serve clients [53]. In another study, nurses' administrative work and data collection were shifted to receptionists, counselling work was shifted to counsellors and community support groups and lab staff took on blood collection [48]. In one study, nurses viewed the establishment of a community health team to enhance services to disadvantaged communities as additional work, particularly in the initial 12-month set-up phase [60]. One nurse in this study said she was concerned that this work was not part of her paid role, highlighting the need for tasks that address the needs of vulnerable groups to be clearly identified and integrated into nurses' roles and appraised.
In another study, substantial increases in nurses' workload associated with the fast scaling up of an antiretroviral therapy (ART) programme in Rwanda were introduced alongside a performance-based financing mechanism [48] where nurses were contracted and remunerated according to their performance. In this study, nurse retention was found to be high which contrasts with the approach taken in other research in Rwanda where nurses did not receive salary increases or other incentives for their new role under this taskshifting initiative [47]. Staffing costs can often be the largest component of a health service; however, another study in Africa found that the provision of multiple nurse-led services via a mobile cervical cancer screening programme was an approach to potentially expand access to health care to rural populations without added costs [46]. Non-financial incentives may therefore be just as important when it comes to delivering quality care. Nurse performance in South Africa has been associated with adequate training, mentoring and support [47]. The nurse's performance in other studies in this review was supported through a range of supervisory and recording mechanisms. Checklists and reporting forms assisted nurses to adhere to guidelines in clinical protocols [46,61,65] while nurses were supervised by senior nurses [59] or their work reviewed by primary care physicians [47,51,62].

Education and training
Education and training activities are described by a number of authors to support nurses and midwives to deliver care. In a study involving nurse-led care to prisoners, nurse education was aimed to enhance the nurses' existing core capabilities and "minimize organizational risk while supporting nurses' role expansion" [59]. In inner city English general practices, a cascade model was employed to train specialist nurse trainers to train and mentor 23 community-based practitioners to deliver an eczema education programme to disadvantaged families [54]. However, high nurse turnover and the high levels of dermatological expertise required to deliver the sessions confidently led to this model being discontinued and replaced with specialist nurse delivery [54]. In a South African diabetes programme, an English expert nurse was employed for the first 12 months of the project to train and support the newly appointed local diabetes nurse [42,45]. Nurse training in the start-up phase of a nurse-led service was also noted in other studies [44,65] along with regular continuing professional education provided by special nurses [62] or doctors [39,61].
Details of physician involvement in nurse training are provided in the studies examining nurse-led ART care in Rwanda [47,48]. In addition to formal training through the National HIV/AIDS programme that involved physician-observed practicums, three nurses received training by doctors at each PHC facility, as well as ongoing supervision and mentorship, before they were allowed to consult patients independently [47]. An additional nurse also received the training at each PHC facility, in order to ensure replacement of staff in the ART service in case of need.
One study in this review involved the pilot of a module on social inclusion/exclusion with a group of nursing and midwifery university students. The study found that the majority of students surveyed on completion of the module held views that were generally positive and inclusive. However, some respondents held stereotypical views potentially compromising their ability to provide health care to vulnerable groups suggesting that ongoing efforts to build empathy and commitment to addressing equity may be required throughout nursing and midwifery undergraduate education [74].

Collaboration
This review identified significant collaborative efforts between nurses and midwives and other health providers and health care organizations, across the community, education and justice sectors, and with communities and consumers/clients/patients. Despite nurses leading the provision of services to vulnerable groups in many studies, they worked with doctors by reviewing patients together [48,51,52,66] or referring when needed [53,62,72]. Papers described nurses also working closely with other nurses [45,60] and midwives working with child and family health nurses [58]. In addition, nurses worked in teams with allied health professionals including physiotherapists, occupational therapists, social workers, dietitians and speech pathologists and non-professional personal support workers [64,65], prison pharmacists [66], dieticians [72] and community support workers [45]. Communication between different professional groups was described as difficult in the early stages of the implementation of a community health team but improved over time when professionals became "aware of each other's public health work, more confident in contacting each other to ask questions, and were beginning to share skills" [60]. Participants in this study reported that interprofessional communication would not have occurred had it not been for the community health team initiative [60].
Collaboration was also found to be central to the ability of nurses and midwives to deliver culturally competent care. In a New Zealand study, nurse communication with families and the acceptability of health care was enhanced through working with interpreter services and grounding their practice in Maori understandings of health [69]. In Australia, the staffing of The Malabar service by midwives who worked alongside Aboriginal Health Education Officers and community health workers helped to ensure community engagement, cultural safety and individualized continuity of care [58]. The importance of collaborating with community health workers to provide appropriate care to pregnant migrant Turkish women is noted in the study by Hesselink and Harting [57] where Dutch midwives and physiotherapists worked with ethnic Turkish community health workers. In addition to increasing the supply of midwives to scale up access in Indonesia, the study by Frankenberg, et al. also described the importance of midwives in developing collaborative relationships with traditional village midwives [41]. These efforts not only aimed to ensure referral to skilled providers but also acknowledged the important cultural role played by traditional birth attendants in supporting women before, during and after birth [41]. In an American study, bicultural/bilingual nurses were employed as part of a diabetes team to provide culturally acceptable care to poor Hispanic patients with type 2 diabetes [72].
The findings of two papers in the review noted the importance of collaboration with the public health sector at the national level and international donors to ensure that efforts to deliver nurse-led HIV/AIDS care are coordinated, well supported and contributed to health system strengthening efforts [47,48]. Collaboration and strategic partnerships with area hospitals, community health centres and public health departments were also described in relation to the operation of a large nursemanaged clinic in America to provide ancillary and specialty health care services to the uninsured [67].
Collaboration and partnerships across sectors were also regarded as a necessary part of care provision. In Germany, The Youth Welfare Services were significant collaboration partners enabling midwives to develop trusting relationships with mothers and provide continuity of care [50]. In other studies, partnership with the voluntary sector [53], police [59] and social workers [73] not only improved the quality of care that vulnerable groups received but also assisted with linking to other services and advocacy efforts. Finally, collaboration with the community is described as a significant component of nursing and midwifery care. This includes nurses undertaking community needs assessments to inform the planning of nurse-managed care to urban Native Americans [67], consultations with community members to inform the development of activities to support networking and social cohesion [56] and working with women [63] and people living with HIV/AIDS who are patients themselves to ensure that all patients received home visits, medications and social support [47].

Discussion
The transition from the Millennium Development Goals to the post-2015 Sustainable Development Goals (SDGs) has provided an opportune window to review heath goals. Global discussions and consultations on the SDGs have focused on the importance of interconnectedness of human development and, in health, on achieving universal health coverage with equity as a central principle. A critical element to deliver that agenda is having a workforce that can deliver accessible health care, including to the poorest, as well as to reach those who are most disadvantaged.
This literature review shows that nurses and midwives have and continue to contribute to providing universal access and reducing heath care disparities through the support of interventions in a number of domains. This paper has conceptualized these interventions using a framework that has highlighted the role of policy and regulation, leadership processes and practices, human resource management, education and training and collaborative partnerships. While in all countries nurses and midwives are currently working towards achieving universal access, most efforts remain undocumented in published literature. Of the 36 papers included, the majority were from high-income contexts with 11 from low-and middle-income countries, of which 10 were from African countries experiencing enormous human resources in health challenges. Only four papers related to midwife-led interventions indicating a gap in knowledge concerning evidence-based policy and workforce interventions in this context. While we were able to identify approaches to increase the number of welltrained, motivated nurses and midwives to provide the services to meet patients' needs thereby increasing access to quality health care services, we were only able to locate one study that identified cost effective nursing care [46]. However, it is not clear if this mobile nursing health service was more affordable to women suffering financial hardship than other services.
The review shows that national and state policies to increase the supply, scope of practice and coverage of nurses and midwives to improve PHC access to address inequity were successful in both low-and high-income countries. Policy was also found to enable nurses to carry out expanded roles. Other authors have called for the need for nurses to pay close attention to the context of legislative and organizational changes in nurse regulation which may constrain nursing's capacity to achieve health equity [76].
In our review, successful initiatives were accompanied by substantial long-term investments in infrastructure, training and improvement of working conditions of the health workforce. Such investment involves health system strengthening as part of efforts to increase universal health coverage which was evident in the context of several studies in this review [41,43,47,48]. A recent study highlights the importance of equity as a measurable component of universal health coverage to ensure health care for vulnerable populations and summarizes useful indicators and frameworks [77]. This will include the ongoing assessment of midwifery and nursing services received by vulnerable groups [78]. However, the effective implementation of policies to increase access to health care requires the active participation of nurse leaders, particularly where the needs of unique populations must be addressed, to promote equity in nursing policy and practice [79,80].
In terms of human resource management, in particular the roles and responsibilities of nurses and midwives, where staff took on expanded roles in their work, there was a positive impact in the delivery of health care. Successful expansion depended on clearly defining roles, providing additional training and supportive mechanisms for taking on these roles. In addition, incentives, both financial and non-financial including opportunities for further training and career development, were shown to be important factors for staff retention and performance that have been highlighted in other literature [81]. In resource-poor settings, the critical analysis of tasks performed by nurses and midwives led to some administrative tasks being assumed by other members of the health team, freeing up nurses and midwives to focus on delivering care especially to those with HIV/AIDS. The review findings concerning support for the expansion of nurses' and midwives' roles and the delegation of tasks to nurses from other cadres and from nurses to other staff concur with research into task shifting and sharing [82,83].
The review found that in terms of collaboration, partnerships and communication that working as members of a health team was key in improving care delivery. Teams were found to work best when there was an understanding and appreciation of the roles and responsibilities among all members of the team, as well as staff with cultural competence and strong relationships with partners. Other literature, not included in this review, provides insight into fostering such collaborative practice through skills building and linkages. Connolly et al. outlines innovative nursing education in communitybased health centres [84], and Sullivan demonstrates how partnerships with community agencies can increase the cultural competency of nurses [85]. These approaches add to the insight provided in the paper by Wray et al. [74] in this review and other reports [86][87][88] where social inclusion and cultural learning positively influenced student nurse clinical and research skills and attitudes. However, more research is required to examine changes in ethical practice and attitudes and the relationship with actual access and uptake of services [89].
The review has several limitations. Despite a structured search of a large number of databases, some studies may have been missed as our keywords may not have been sufficient to retrieve them. The use of a conceptual framework assisted in focusing the analysis, but detail may have been lost in an effort to produce a comprehensive synthesis of useful insights for nurses, midwives and decision makers.

Conclusion
This review has synthesized literature documenting the interventions and approaches to support nurses and midwives to provide universal access to PHC for disadvantaged populations. While much is being done in many countries, few collect data or conduct operational research to document the challenges being faced or the strategies used to retain nurses and midwives to work with vulnerable populations. It is critical that nurses and midwives, especially in LMIC, be encouraged to document best practices and publish these so that knowledge can be shared. A conceptual framework for nursing and midwifery leadership and workforce interventions may be useful for not only documenting lessons learned but also designing, planning and evaluating these experiences and their impact on universal health access particularly for vulnerable populations. Such guidelines may help to focus efforts to reduce health inequity and achieve universal health coverage.