Facilitators and barriers to the sustainability of universally accessible parental training interventions: a systematic qualitative review using normalization process theory.

Background: Universal parenting programmes aim to strengthen parent-child relationships and support parental well-being during the transition to parenthood. While these programmes can improve parental confidence, self-efficacy, and child social-emotional development, achieving sustained delivery in routine practice remains a major challenge. Understanding the factors that facilitate or hinder their implementation is essential for optimizing their public health impact. This review synthesizes qualitative evidence on barriers and facilitators to the implementation and sustainability of universally accessible parental training interventions. Methods: We conducted a systematic qualitative review following PRISMA guidelines. Ten databases (PubMed, PsycInfo, SocIndex, CINAHL, Embase, Medline, Sociological Abstracts, ERIC, Scopus, and Web of Science) were searched in May 2024, and updated in July 2025, for peer-reviewed qualitative studies published after 2003 in English. Studies were eligible if they evaluated universal parenting interventions in high-income countries and explored aspects of implementation or sustainability. Interventions targeting specific clinical populations were excluded. Data extraction was conducted by multiple authors, and reporting transparency was assessed using the Consolidated Criteria for Reporting Qualitative Research (COREQ). Findings were synthesized using Normalization Process Theory (NPT) to identify how interventions become embedded in practice. Results: Eight studies from six countries were included, covering interventions delivered in primary care, community health, and web-based settings. Across NPT constructs, key facilitators included strong stakeholder engagement, peer and managerial support among participants, and flexible delivery models that fit local contexts. Recurrent barriers were limited time and resources, insufficient training and weak managerial or policy support. Parent engagement was sometimes constrained by perceptions of limited programme relevance or logistical obstacles, highlighting the importance of clear communication and iterative adaptation to local needs. Conclusions: Universal parenting interventions can contribute to improved parental and child outcomes when effectively integrated into routine practice. Sustainable implementation depends on early co-design with stakeholders, alignment with existing health services, and sustained managerial and policy support. Embedding feedback loops and mechanisms for adaptation can strengthen engagement and ensure that interventions remain feasible and relevant over time. Future research should focus on strategies to enhance reach and to assess long-term population-level effects on child well-being. Systematic Review Registration: https://www.crd.york.ac.uk/PROSPERO/view/CRD42024559474, identifier CRD42024559474.