The more you do it, the easier it gets: using behaviour change theory to support health care professionals offering reproductive genetic carrier screening

Recent advances in genomic sequencing have improved the accessibility of reproductive genetic carrier screening (RGCS). As awareness and interest grows, non-genetic health care professionals are increasingly offering RGCS to consumers. We conducted a qualitative interview study informed by behaviour change theory to identify influences on health care professionals considered as ‘early adopters’ offering RGCS through Mackenzie’s Mission, an Australian national research study investigating the implementation of free RGCS to couple’s preconception or in early pregnancy. Interviews were deductively analysed using the Theoretical Domains Framework to examine barriers and enabling factors. In total, we interviewed 31 health care professionals, who were primarily general practitioners (n = 23) offering RGCS through Mackenzie’s Mission. Upon analysis, 15 barriers and 44 enablers to implementation were identified and categorised across three health care professional target behaviours 1. Engaging with RGCS, 2. Identifying eligible patients, and 3. Offering RGCS. Whilst all Theoretical Domains Framework domains were present, barriers were predominantly categorised as ‘Environmental Context and Resources’ e.g., lack of time, followed by ‘Knowledge’ e.g., lack of understanding about genetics and ‘Beliefs about Capabilities’ e.g., concern about giving high risk results to patients. Although health care professionals expressed a preference for offering RGCS through a comprehensive and supported model of care, such as Mackenzie’s Mission, barriers remain. By understanding what drives current health care professionals’ behaviour towards offering RGCS, behaviour change theory provides an avenue to direct future efforts based on evidence and improve service delivery.


INTRODUCTION
Reproductive genetic carrier screening (RCGS) allows prospective parents to gain knowledge of their chance of having children with a serious autosomal-recessive or X-linked genetic condition. When a couple are both found to be carriers of a condition, they have an 'increased chance', of having an affected child [1]. As such, screening is offered preconception or in early pregnancy to facilitate greater reproductive choices [2]. Recent advances in technology have increased affordability of RGCS moving from single-gene testing e.g., Tay-Sachs disease [3] to allowing screening for multiple conditions (i.e., 'expanded' screening) driving international recognition of the benefits to population wide screening [4,5]. In Australia, RGCS is predominantly available commercially to individuals or couples, however the cost and lack of public and medical practitioner awareness of screening exacerbates inequities of access and outcomes across populations [6,7]. In response, and to reflect changing practice guidelines, some national health systems (e.g., Australia, Belgium) have started investigating population level RGCS [3].
Expanding the availability of RGCS requires non-genetic health care professionals e.g., general practitioners (GPs), obstetricians, fertility specialists and midwives to play an important role in offering RGCS. Decades of single-gene screening have provided a rich foundation of knowledge about health care professionals' (HCPs') perceptions towards offering population-based screening for individual conditions [8][9][10]. However, research examining expanded carrier screening has been limited primarily to genetic HCP or secondary HCP perspectives e.g., gynaecologists and obstetricians [11,12] or focused on hypothetical offering in the primary healthcare setting [13,14]. A recent review identified a predominance of practitioner level barriers (i.e., lack of practitioner confidence, interest) and organisational level enablers (i.e., professional bodies providing consistent advice) [15].
An in-depth understanding of this area is hampered by a lack of targeted implementation research examining the implementation of RGCS at a population scale. The introduction of new practices, such as offering RGCS, requires a change in practice of the HCPs. Behaviour change theory provides a way to analyse what is driving current behaviours (i.e., current practice) of HCPs and identify interventions that support the new desired behaviour [16]. Theory informed frameworks such as the 'Capability, Opportunity, Motivation and Behaviour' (COM-B) model and associated Theoretical Domains Framework (TDF) are effective for understanding contextual influences on desired behaviour [17]. The COM-B framework posits that behaviour is a result of our capability (C) (can we do the activity), opportunity (O) (is it possible to do it) and our motivation (do we want to do it) (M). The TDF consists of 14 domains and provides a more granular understanding of the influences on behaviour. For example, several TDF domains influence motivation (e.g., Emotion, and Belief about Consequences) and therefore align with the COM-B domain motivation (Fig. 1).
In this study, we use qualitative methods informed by behaviour change frameworks, to investigate the experience of early adopters of RGCS in the context of a national research programme. Our objective is to gain an insight into HCPs' perceived barriers and enablers to offering RGCS.

MATERIALS AND METHODS Context
This study is part of a larger implementation science programme investigating strategies to support RGCS implementation in Mackenzie's Mission. Mackenzie's Mission is an Australian Government funded research study investigating how to optimally implement an easily accessible RGCS programme in Australia by offering couples free RGCS, testing over a thousand genes [18]. Details of the study are published elsewhere [18] but briefly couples were directed to the Mackenzie's Mission website via an initial conversation with their GP, obstetrician, midwife, fertility specialist or genetics HCP. The portal contained information, a decision support tool and how to register. If the couple proceeded, they collected and posted in a cheek swab. HCPs were not included in this process but were informed of results.

Research design
We employed a qualitative approach using semi-structured interviews with a subset of participating HCPs to gain a rich understanding of the meanings and interpretations behind individuals' behaviour towards offering RGCS through Mackenzie's Mission [19]. We adopted descriptive phenomenology which can be used to study an area of interest from the perspective of those involved [20], using behaviour change theory as our methodological framework.

Participants and recruitment
Throughout the study duration, HCPs from various settings in all Australian states and territories (including general practices, private/public obstetrics and midwifery practices, fertility clinics, and community health services) were able to self-refer into the Mackenzie's Mission study or were invited by study genetic counsellors. As the focus of the study was on preconception RGCS, the intention was for most couples to be recruited via GPs. HCPs who agreed to be part of Mackenzie's Mission were provided with an education session about RGCS and the study processes before being able to offer Mackenzie's Mission RGCS to their patients.
HCPs who expressed interest via a pre-education questionnaire and had been offering Mackenzie's Mission for >8weeks were contacted via email, by the implementation research team, and invited to take part in either a telephone or videoconference interview. One follow-up invitation was sent for those who did not respond to the initial contact. Using purposive sampling [21], we selected over 150 eligible HCPs (n = 168) to invite to take part in an interview. HCPs were from a range of professions and levels of experience of RGCS, in particular GPs as the predominant referrers, and different state/territories. Those HCPs who declined to participate in the Mackenzie's Mission study were also offered an opportunity to interview.

Data collection tools and procedures
An interview guide (Supplementary File 1) was developed using the behavioural framework COM-B, as a way to categorise sources of behaviour [22]. For example, 'what experience do you have with RGCS?' (C); 'Starting off, was there anything that would have made offering RGCS easier?' (O); and 'What made you decide to offer RGCS?' (M). Participants were asked about their experiences of offering RGCS and their views on future RGCS service planning. Whilst the structure of the guide remained the same, constant iterative comparison [23] of the interview transcripts led to minor revisions in the interview schedule. Interviews were designed to take around 30 min, and scheduled at a time convenient for the HCP. Interviews were disrupted by the SARS-CoV-2 pandemic and began in August 2020, finishing in August 2021 when data saturation and maximum variation in sample was reached. Interviews were conducted by three qualitative researchers (SB, JL and ZF) who had no prior relationship with participants. All interviews were audio-recorded, de-identified and transcribed verbatim. Audio-recorded verbal consent was sought and recorded before the interview.

Data analysis
Interview data was managed in NVivo 12 [24]. Analysis was guided by the TDF. A coding guide that incorporated the TDF was adapted to the specific context (Supplementary File 2), revised from a previously published guide [25]. An important first step to using the TDF is to define the target behaviour i.e., the core activity that is essential for a change in practice to occur. For this study 'offering RGCS' was identified. However, during analysis, two additional target behaviours became evident. 1. Engaging with RGCS-how HCPs initially start thinking about offering RGCS; 2. Identifying eligible patients to offer RGCS to-including pre-conception; and finally the original target behaviour, 3. Offering RGCS to patients-incorporates the discussion with potential patients their perceived receptivity and following required process. Transcripts were examined and deductively coded using the coding guide (Supplementary File 2) to identify factors that facilitate or hinder HCPs when offering RGCS. Initially, five transcripts were coded independently by two researchers (SB and ZF) and compared for discrepancies. One researcher (ZF) completed the coding with ongoing regular meetings (SB and JL) to discuss and resolve challenging coding and findings. Reflecting the complexity of offering RGCS, overarching barriers were identified first before detailing the underlying barriers and determiningtheir associated TDF coding (SB, ZF and JL).

RESULTS
Participant characteristics are presented first, followed by the analysis of the three target behaviour barriers and enablers and associated TDF codes.

Characteristics of participants
Overall,~1000 HCPs were enroled in the Mackenzie's Mission study. Of the 168 eligible HCPs invited to an interview, thirty-one agreed. The few participants who actively declined and gave reasons noted they were too busy especially because of the SARS-CoV-2 pandemic or they had not offered RGCS due to seeing different patient cohorts. No HCP who declined to participate in Mackenzie's Mission indicated they were available for a follow-up interview. On average interviews ran for 24 min most were undertaken via videoconference and one participant opted for a telephone interview. Table 1 summarises the characteristics of interview participants who were predominantly GPs (74%) working in metropolitan areas of Australia (84%) with a fair proportional distribution amongst states per population size. Most participants had prior experience of offering RGCS (68%) and eight (26%) had experienced a patient receive an increased chance result as part of the Mackenzie's Mission study.

Barriers and enabling factors by target behaviour
From the interviews, 15 barriers and 44 enablers (6 of which related to specific programme components of Mackenzie's Mission) were identified across the three target behaviours 1. Engaging with RGCS, 2. Identifying eligible patients to offer RGCS to, and 3. Offering RGCS to patients. Whilst all TDF domains were present, barriers were predominantly categorised as 'Environmental Context and Resources' followed by 'Knowledge' and 'Beliefs about Capabilities' (Fig. 2). Here, we outline the barriers and report recurrent enablers as reported by participants, further details are reported in Tables 2-4.
Target behaviour 1: Engaging with RGCS Two overarching barriers were identified: awareness, understanding and education about RGCS and HCPs' attitudes towards and beliefs about RGCS. Figure 2 and Table 2.
Awareness and understanding of RGCS: Three barriers were associated with a lack of, or low knowledge of, RGCS within primary health care. Consequences) e.g., patient anxiety about screening or financial implications for families who receive an increased chance result. However, emotional connection acted as an enabler (TDF: Emotion).

Target behaviour 2: Identifying eligible patients
One overarching barrier was identified in this target behaviour, opportunities to identify eligible patients. Figure 2 and Table 3.
Opportunities to identify eligible patients. . Some HCPs were mindful about raising anxiety for women they see in early pregnancy assessment clinics or ensuring they take patient's cultural beliefs into consideration. Some reflected on their messaging to be clear that preparing if a child may require early intervention or have special needs can be helpful. Being able to build rapport with patients through continuity of care allowed HCPs (especially midwives) to judge each situation on a case-by-case basis (TDF: Skills) and ensure RGCS was offered, or even just mentioned as an option to patients regardless of their situation.

Target behaviour 3: Offering RGCS to patients
Two overarching barriers were identified in this target behaviour, providing pre-and post-test counselling, and patient receptivity. Figure 2 and Table 4.
Providing pre-and post-test counselling. HCPs reported four interrelated barriers to counselling during these phases.
i. Low consumer awareness (TDF: Environmental Context and Resources). HCPs reported low consumer awareness of RGCS and patient confusion with other prenatal tests (i.e., NIPS). Consequentially, HCPs described a sense of responsibility to take the time to increase awareness and explain in an easily digestible way what RGCS involves and considered themselves well placed to at least raise the topic (TDF: Social and Professional Identity). ii. Concern about ability to counsel (TDF: Belief about Capabilities) were reported by some HCPs especially when not regularly providing pre-and early pregnancy care including, mixing up RGCS and NIPS or raising potentially worrying or distressing information. Genetic counsellors were favoured as a resource for HCPs to seek guidance, others sought peer advice (TDF: Social Influences), and some felt practice was key (TDF: Skills Patients' religious beliefs, or patients with ethical concerns around termination of pregnancy were discussed by some HCPs. In most circumstances, HCPs felt they could still provide patients with the information that allowed them to make an informed choice in line with their values, framing the conversation around the benefits of knowing your carrier status (awareness and preparedness, becoming knowledgeable about the condition, talking to specialists, joining support groups etc.) (TDF: Skills). iii. Not knowing whether the sample has been supplied (TDF: Environmental Context and Resources). Some HCPs ant to be made aware when a couple provided a sample to the laboratory for screening to accommodate follow-up appointments. Here, HCPs could follow-up with the patient if required (TDF: Reinforcement).

DISCUSSION
To support any change in a behaviour or activity, such as offering RGCS, it is essential to clearly specify the target behaviour(s) required and the associated barriers and enablers at each stage. Without this understanding there is a risk of investing resources to design solutions for potentially non-existent problems, wasting time and effort [26]. This study investigated the experiences of HCPs, with particular focus on non-genetic professions, offering population RGCS and categorised findings into three sequential target behaviours: 1. Engaging with RGCS, 2. Identifying eligible patients to offer RGCS to, and 3. Offering RGCS to patients. We identified 15 associated barriers and significantly more enablers (n = 44) which could reflect the nature of the participants, who as early adopters are often positive about the change and are understood to influence the behaviour of those around them by making the behaviour change more observable [27]. Indeed,   Professionally, not a lot of midwives would understand, or maybe see the need for pregenetic testing because they just see the normal births that come through and don't realise the complications. MW04 Not every GP should have to do it because if someone does it, they should probably do it well, and they should probably know the landscape of different offerings, as opposed to, 'this is the only test I know, and it will cost you $1000' GP13 In my practice of around eight doctors, I'm the main provider of antenatal care so I find it can be tricky a little bit when your colleagues don't have the same interest too, so the levels of confidence and experience in providing reproductive carrier screening counselling varies quite a lot throughout GPs and they're the main group of people that I have regular contact with. GP11 Well-placed in primary healthcare TDF: Social Professional Role and Identity It fits in so nicely with our current focus on preconception counselling, which I think is the domain of the GP and targeting the woman even before she starts embarking on her reproductive course. I think the GPs are the ones who should be actually focusing on this and providing this, and it comes naturally to us…I think to make it really successful it should be in primary care, and the RACGP guidelines they are actually encouraging us to offer it, so they've embraced it, so as primary care providers we should be embracing it. GP06 Other professions who could offer or be aware of RGCS TDF: Social Professional Role and Identity We [clinical geneticists] can be later on, we can be a second tier and we can tell them this is available, but it should actually come from a grass root level because that is where you would be capturing most of the population, we see a very niche population. So, for it to be most effective, it should be started at the level of the GPs. We can always be involved. CG16 You could certainly target fertility clinics, practise nurses are a good idea actually because I think that GPs that have practise nurses, that could definitely be in their scope. If you are looking to bring it into nursing and midwifery the gyn nurses, but midwifery itself, no. MW08 School nurses should be involved like the Jewish screening programme. CG09 I'm a no door is the wrong door kinda gal. I don't care if you are a midwife, I don't care if you are an obstetrician, a social influences were shown in this study to be a principal factor in HCPs' initial engagement with RGCS and increasing awareness amongst their peers and will play a key role in the success in the roll out of future population RGCS programmes. Acknowledging previous research undertaken in this area, here we discuss HCPs' preferred option for offering RGCS through a comprehensive model of care, like the approach taken in Mackenzie's Mission, the associated challenges and identify implications for future service delivery. TDF domains are indicated with bold text.
The Mackenzie's Mission model of care required HCPs to provide the offer of testing and direct the couple to a study participant portal. There the couple were provided with education and a decision aid to make informed decision about RGCS. Although this approach was designed to minimise the time taken for HCPs to offer RGCS, it meant HCPs lacked knowledge of the patients' journey and did not know whether the patient had in fact accepted the offer of screening. Understanding their role in the process appeared key to HCPs improving belief about their capabilities in incorporating this more 'hands off' way to offering RGCS into their practice. Some HCPs hoped the model, especially the online education and consent which is favoured for overcoming the complexities of consent in genomic medicine [28], would continue when RGCS becomes more widely accessible.
Equity was raised by many participants. We did not capture data on HCP ethnicity which may have provided a useful lens with which to analyse some HCP comments and assumptions on when to offer RGCS or not. Some HCPs expressed concern about when it would be appropriate to offer screening for some communities e.g. migrant populations. There is the risk of unconscious bias acting as a barrier to equity of access through the offer, or lack of to RGCS. Whilst no access to technology barriers were reported, several HCPs raised concerns about potential consequences due to language barriers for couples from culturally and linguistically diverse backgrounds being able to access online material without HCP assistance [29]. The availability of online translation services may help overcome these concerns [30]. Overall, the ease of We were just ready for it, so genetic services were happy to recruit. And I guess also fortunately our laboratory was keen to be involved. CG17 ii HCP concern about possible negative consequences (anxiety,  Pre-planning which patients might be eligible TDF: Behaviour Regulation I do a bit of a handover on the families coming in for that clinic, and I'll look at their history and their situation access was found complimentary to telehealth and an acceptable way to offer RGCS for regional/remote areas. The model also worked for donor couples, where the donor could provide a sample, allowing HCPs to be able to offer equitable care. Accessing RGCS through Mackenzie's Mission still requires HCPs to have the knowledge and skill to identify patients for whom RGCS is appropriate. Within the Mackenzie' Mission programme an extensive amount of work has been conducted and reported on the role (and design) of education in the implementation of genomics and large-scale carrier screening programmes. Despite widespread consensus that RGCS is best situated in primary care, aligning with HCPs' professional identity, and offered preconception [2,7,31], research shows higher uptake among pregnant women [32]. Not only does offering pre-conception allow couples access to greater reproductive options, but our study also indicates offering in pre-conception lessens other HCPs barriers (e.g., environmental time constraints in antenatal appointments, and HCPs concern about the potential consequences for patient anxiety). However incorporating the offer of RGCS into pre-conception care (public funding capped at 40 min) appeared to be more challenging, due to a lack of resources and forgetting to offer due to competing priorities in short appointment sessions with HCPs finding it easier to discuss RGCS when the conversation is initiated by the patient [9]. This lack of time will remain a key challenge and identifying mechanisms to support HCPs will be essential to drive successful take up and implementation of future RGCS programmes. Undoubtedly, raising community awareness of RGCS as a part of pre-conception care is needed to facilitate greater patient receptivity and ability to make informed decisions about screening. As patient health literacy was considered an enabler for HCPs to offering RGCS, increasing consumer awareness may also improve equity of access. HCP skill and intentions to incorporate RGCS into general practice appointments was an attributable factor to opportunistically identifying pre-conception patients. Although HCPs found raising RGCS in early pregnancy easier, some HCPs expressed concern about the consequences with the potential of upsetting the couple during this period. Fears of medicalising pregnancy have previously been identified [13,33] and additional tools (e.g., decision aids [34]) are required to ensure couples can make decisions that align with their values [32].
Unlike the other target behaviours, HCPs did not recognise any Mackenzie's Mission specific supports provided for the second target behaviour, identifying eligible patients. Where enablers are lacking, often in more complex areas (e.g., forgetting to offer RGCS pre-conception-TDF Memory Attention and Decision Making) the application of the behaviour change theory, through coding with the TDF [35], can offer additional theory informed behaviour change techniques using the Theory and Techniques Tool [https:// theoryandtechniquetool.humanbehaviourchange.org/] [36] to support HCPs. For example, theory informed behaviour change techniques aligned with Memory, Attention and Decision Making include 'prompts and cues', e.g.,, setting a reminder on the GP information system to prompt the 'One Key Question®' [37] discussion with all patients of reproductive age to ask if they are planning a pregnancy in the near future. If yes, the HCP can share a range of health considerations including the option of RGCS.
One reported area of concern was the need for counselling couples who receive a 1 in 4 chance of affected children with HCPs' belief about their capabilities. The Mackenzie's Mission model ensured a study genetic counsellor was available and they played a critical role in supporting HCPs with expert knowledge and skills, and also couples, as they made reproductive decisions to align with their values. Further provision of RGCS through primary care will require careful consideration of how genetic counselling services could be provided [34,38,39]. Given HCPs perception of their own ability of offer RGCS appears to be contingent on availability of iii HCPs being mindful of patients' personal situation TDF: Beliefs about Consequences There are some that I just won't mention it at all, I just think it's too much for them [women seen in early pregnancy assessment clinics]' GP22 Sometimes it's a bit too much for them [migrant populations], and then they take away all the information and they don't do anything about it, so rather than putting somebody unnecessarily through so much turmoil, we can pick and select our patient population. GP06 Less and less but sometimes we do see their religious beliefs do not allow them to pursue science in a way we would like them to…So if there is a clear understanding that it is going to be a no, then I would not offer it. CG16 Building patient rapport TDF: Skills There are some where there is more than one consultation, I might mention it at the final consultation like 'just to let you know this is something that is available should you be interested.' GP22 A majority of the time I've met them on the wards, so I'm not an unfamiliar face…and I've already built some sort of rapport with them, and I can sit down with them and say, 'look, if you are planning future pregnancies this is something that you might want to consider for yourself.' MW04 It comes down to that poor time allocation we get given with our client face-to-face and therefore it needs to be raised at that social media level, whether it be radio, flyers, Facebook whatever format you can think of. SHNurse20 Raising the profile [through MM] has been helpful, I think it has made having the conversations easier.
Among my colleagues as well as consumers and among midwifery staff. GP25

Word of mouth TDF: Social Influences
It's awareness and whether they have got friends that have done the same test before. I think a lot of people now rely of social media and their friends to tell them…or convince them rather than us health professionals. GP24 ii HCP concern about pretest counselling   Sometimes there are people like them who are worried because in Islam we don't do a termination very easily…but I said 'look even if you don't go for a termination, it sets you up so that you expert genetic counselling and clinical support, it is essential that population-based programmes provide this support.
In addition to HCP individual level experiences noted here, future implementation of national RGCS programmes while dependent on local context [40] may benefit from aspects of programme design. Figure 3 reports several features identified from this study that can contribute to making reproductive genetic carrier screening more accessible.

Limitations
Drawing on the experience of early adopters is likely to have introduced positivity bias, with the possibility that HCPs who were likely to respond to interview invitations were those most likely highly engaged with Mackenzie's Mission. Mitigating that, a third of participants had no previous experience with RGCS. Of the 168 potential participants we only interviewed 31 either due to lack of response or the HCP was unable to participate. We were also are aware of what happens afterwards' . GP18 I might mention that so it's not necessarily that you would terminate the pregnancy but you might choose to learn a bit about the condition, to talk to specialists, to join a support group, peer information and that sort of thing. GP25 Patients taking up the offer TDF: Reinforcement All but two people I've discussed it with have ended up taking up the opportunity, which is really good. GP26 The reason people chose not to was they either came from a faith tradition where that was not something they wish to enquire about or even if they didn't have a faith background tradition, it was just they didn't know what they would do with that information and they were aware it was going to create angst and issues for them. GP25 Sense of reward for offering RGCS TDF: Reinforcement It's fantastic, everyone's been excited about do it, in fact one of my couple's is already pregnant, have just come in today because they're pregnant, so that's very exciting. GP01 iii Not knowing when patient's take-up testing TDF: Reinforcement I don't know who actually decides to do it until I get their result, however long later. GP02 Altered when patient supplies a sample TDF: Reinforcement We know how many forms we've given out and slowly the results trickle in but getting an idea of how many of your patients have taken up the screening is nice to know. GP07

Purpose Example
Comprehensive model of care To maximise support given to health care professionals and paƟents Clear guidance for paƟents and professionals on purpose, procedure and outcomes from reproducƟve geneƟc carrier screening.
Appropriate paƟent informaƟon and support To simplify the role of the Health Care Professional and maximise a couples' ability to make decisions about screening that align with their values Online paƟent informaƟon with decision aids and online translaƟon Increase community awareness of reproducƟve geneƟc carrier screening To facilitate offering screening preconcepƟon WaiƟng room posters prompƟng discussion with health care professionals about pre-concepƟon care, educaƟon campaigns Health care professional reminders (on electronic record systems) To facilitate remembering to offer reproducƟve geneƟc carrier screening to all eligible paƟents Alert in electronic record systems for paƟents of reproducƟve age and accessing other health intervenƟons related to reproducƟon and/or introducing a rouƟne clinical intervenƟon e.g., One Key QuesƟon ® "Are you planning to have children in the future?" to prompt further discussion about preconcepƟon care (including RGCS).
Support for non-geneƟc trained health care professions to safely and appropriately return high chance results To support healthcare pracƟƟoners to sensiƟvely deliver increased chance results to paƟents and to understand the appropriate pathways for referral to geneƟc services.
Access to geneƟc counsellors for couples with high chance results Training from geneƟcs services in the delivery of increased chance results and provision of informaƟon about pathways for referral to geneƟcs services. Fig. 3 Examples of aspects of programme design that can contribute to reproductive genetic carrier screening being more accessible.
unable to capture the views of those who declined to participate in the Mackenzie's Mission study. The SARS-CoV-2 pandemic led to data collection taking over a year, which was longer than planned, meaning some external contextual factors may have changed. This study was undertaken in the context of an Australian Government funded research project where generalisation may be limited to Australian health system and a well-resourced research project (under Mackenzie's MIssion, RGCS is offered free of charge to the couples, genetic counselling is offered to couples receiving a high-chance result and to support HCPs so may not reflect other health systems or state-wide or national RGCS programmes. At present, RGCS is offered in an ad hoc manner and access is variable. Whilst population-based approaches will make access more equitable, targeted support for HCPs to offer patients the option of RGCS is required. Behaviour change theory provides a structured approach to learning from the experience of early adopters and an opportunity to identify the determinants influencing implementation. The key steps of collection and coding of barriers and enablers by each target behaviour identified outlined here can now be used to select and test theory informed implementation strategies. Although this study shows HCPs' strong preference for offering RGCS through a comprehensive model of care, and various other programme design elements that reduce barriers, it is essential that future research continues to leverage behaviour change theory to develop and test programme design elements that contribute to RGCS being provided in an equitable and accessible way.

DATA AVAILABILITY
The datasets generated during and/or analysed during the current study are available from the corresponding author on reasonable request.