Application Usability, Engagement, and Postpartum Weight Retention: Secondary Analysis of the INTER-ACT Randomized Controlled Trial.

Objective: To examine whether perceived usability of the INTER-ACT application influences postpartum weight loss and whether this effect is mediated by application use, motivational power, and implementation of lifestyle recommendations. Patients and Methods: Dutch-speaking women aged 18 years or older who had delivered a singleton infant and exceeded the recommended guidelines of the Institute of Medicine for gestational weight gain got recruited from May 2017 to April 2019, Across 6 Flemish hospitals. This secondary analysis included 138 participants of the INTER-ACT intervention arm. At 6 months postpartum participants completed a process evaluation survey, assessing application usability using the system usability scale, perceived motivational power, and perceived implementation of lifestyle recommendations. Weight loss was calculated between 6 weeks and 6 months postpartum. Pearson correlations and parallel mediation analyses were conducted, adjusting for maternal age, parity, and prepregnancy body mass index. Results: Application usability was moderate (mean system usability scale=60.6) and positively associated with perceived application use frequency (B=.05, Conclusion: Application usability was associated with engagement and positive emotional experience, but not with reduced PPWR. The GWG remained the main determinant of postpartum weight outcomes. Preventing excessive GWG and complementing this with emotionally supportive postpartum mHealth tools may improve outcomes. Trial Registration: clinicaltrials.gov Identifier: NCT02989142.