Introduction: The postpartum period goes along with an increased risk of unhealthy weight gain and numerous physical and psychological challenges, which are associated with mental well-being and resilience. Given the individual circumstances and the accompanying time constraints, evidence-based mHealth interventions may be useful for flexible, spot-on complementary care. Thus, the mHealth app I-PREGNO aims to enhance mental well-being and resilience by offering cognitive-behavioural and behaviour change skills training to prevent unhealthy weight development in this vulnerable life episode. In a randomised controlled trial, we will examine its effectiveness and acceptance.

Protocol: Parents of infants between 0 and 12 months will be randomised to the intervention or control group. Both groups will take part in a baseline survey (t0) and further assessments after 12 weeks (intervention duration, t1), and 6 months (t2). The intervention group will use the self-guided mHealth app after t0 and both groups will get unlimited access after t2. The primary outcomes will be i) weight (difference of weight in kg after the intervention and pre-pregnancy); ii) mental well-being assessed through the Edinburgh-Postnatal-Depression-Scale and Parenting Stress Index; iii) resilience assessed through the General Self-Efficacy Scale and Difficulties in Emotion Regulation Scale. Secondary outcomes will be sociodemographic variables, eating behaviour, physical activity, relationship experiences, childhood trauma, postpartum bonding, regulatory disorders, and app usability. Gender differences between mothers and fathers will be considered.

Conclusion: Positive effects on weight development in the postpartum period, mental well-being, and resilience due to the I-PREGNO intervention will support parental health in the critical postpartum phase. The study results will contribute to the growing field of evidence-based, highly scalable, low-cost, geographically independent, just-in-time mobile support for a target group that is restricted in time and resources.

Trial registration: The trial has been registered at the German Clinical Trials Register (DRKS00031067) in January 2023 prospectively.