Behavior change techniques in pregnancy dietary interventions: a systematic review through the lens of the COM-B model

Pregnancy presents a critical "teachable moment" for promoting healthy dietary behaviors, with significant implications for maternal and neonatal outcomes. However, achieving sustained dietary behavior change remains complex. This systematic review aimed to examine the effectiveness of dietary interventions during pregnancy and explore the underlying mechanisms of behavior change, focusing on behavior change techniques (BCTs) through the lens of the COM-B model. This review was conducted following the PRISMA 2020 guidelines and employed a narrative synthesis approach. A comprehensive search of six electronic databases and grey literature sources was performed. Studies were eligible if they evaluated dietary interventions targeting pregnant women and reported outcomes related to eating behavior or gestational weight gain. Forty-five studies met the inclusion criteria. Intervention components were coded using the Behavior Change Technique (BCT) Taxonomy V1. Risk of bias was assessed using the Cochrane tool for randomized controlled trials and ROBINS-I for non-randomized studies. The review revealed mixed findings regarding the effectiveness of dietary interventions, largely due to substantial heterogeneity in intervention designs, delivery methods, and outcome measures. Commonly employed BCTs included goal setting, action planning, knowledge shaping, and feedback. Most interventions targeted psychological capability and reflective motivation, while fewer addressed social opportunity and environmental restructuring. Current dietary interventions predominantly focus on enhancing individual motivation and capabilities but often overlook social and environmental barriers. Future research should design interventions that incorporate broader COM-B dimensions, address health literacy disparities, and tailor strategies to participants' contextual needs. A deeper understanding of behavior change mechanisms may enhance the effectiveness and sustainability of dietary interventions during pregnancy. Registered on PROSPERO database (CRD42022310860).