'Healthy Eating and Lifestyle in Pregnancy (HELP)' trial: Process evaluation framework

We developed and tested in a cluster RCT a theory-driven group-based intervention for obese pregnant women. It was designed to support women to moderate weight gain during pregnancy and reduce BMI one year after birth, in addition to targeting secondary health and wellbeing outcomes. In line with MRC guidance on developing and evaluating complex interventions in health, we conducted a process evaluation alongside the trial. This paper describes the development of the process evaluation framework.

This cluster RCT recruited 598 pregnant women. Women in the intervention group were invited to attend a weekly weight-management group. Following a review of relevant literature, we developed a process evaluation framework which outlined key process indicators that we wanted to address and how we would measure these. Central to the process evaluation was to understand the mechanism of effect of the intervention. We utilised a logic-modelling approach to describe the intervention which helped us focus on what potential mediators of intervention effect to measure, and how.

The resulting process evaluation framework was designed to address 9 core elements; context, reach, exposure, recruitment, fidelity, recruitment, retention, contamination and theory-testing. These were assessed using a variety of qualitative and quantitative approaches. The logic model explained the processes by which intervention components bring about change in target outcomes through various mediators and theoretical pathways including self-efficacy, social support, self-regulation and motivation.

Process evaluation is a key element in assessing the effect of any RCT. We developed a process evaluation framework and logic model, and the results of analyses using these will offer insights into why the intervention is or is not effective.