Table 3 Overview of the study design fidelity strategies and monitoring plan for HeLTI SA

Ensure intervention is congruent with relevant theory and practice

Operationalize treatment to optimally reflect theoretical roots and define variables relevant to the “active ingredients” of the intervention

- Health helpers encouraged to use HCS and SMARTER planning in all intervention sessions.

- Behaviour change techniques incorporated into the intervention health literacy resources.

- Health monitoring, feedback, and action (e.g. referral) are in line with the current practice in South Africa.

- Health helper self-reflection of HCS use is reported on REDCap and monitored by project coordinators.

- Several intervention sessions are recorded and evaluated according to a pre-determined checklist.

Ensure a similar dose within the intervention group and across phases

Ensure that intervention “dose” (measured by number, frequency, and length of contact) is adequately described and is similar for each participant and across different phases.

- Length, number, and frequency of contact sessions are outlined in the intervention protocol (Fig. 1).

- Intervention duration is based on the four fixed phases outlined in the intervention protocol; the preconception phase length is dependent on participant pregnancy.

- Individual session duration is dependent on participant needs and expected to be diverse.

- An intervention manual per phase has been developed.

- Monthly contact and level of contact are consistent across all intervention phases.

- Project coordinators monitor the frequency and number of intervention sessions via electronic activity log on REDCap.

- Notes section is available at the end of the activity log to document and review the unique information about the participant or session.

- The health helpers monitor the progress with SMARTER goal planning in each session.

-Quarterly quality assurance reports.

Plan for setbacks

Address possible setbacks in implementation (e.g. intervention providers dropping out).

- New health helpers are hired when necessary and are dependent on funding.

- Details of the potential suitable future health helper candidates are kept on file.

- Attrition of health helpers is recorded and flagged by human resources and project coordinators.