English: "At the individual level, attributes and interactions specific to mothers and infants, such as mental health challenges, anxiety about unsettled infant behaviours, self-reported insufficient milk (SRIM), and low self-efficacy are challenges to breastfeeding that have not been adequately addressed within health systems to date.

This Series provides a new vision on how to address breastfeeding protection, promotion, and support at scale through multilevel, equitable approaches. This vision addresses breastfeeding barriers and facilitators across all levels, from the structural to the individual, building on the conceptual model of the 2016 Lancet breastfeeding Series (figure 1). In this Series paper, we examine how individual-level parent and baby attributes interact with breastfeeding determinants at other levels of the socioecological model, how these interactions drive outcomes, and what policies and interventions are necessary to achieve optimal breastfeeding. Structural and settings-based barriers to breastfeeding, including commercial determinants, are expanded on in the second and third papers of this Series, which analyse the marketing of commercial milk formula and the political economy of infant and young child feeding (figure 1)."

"The papers in this Series were developed with a combination of research methods: (1) analysis of national representative survey data of children younger than 2 years, (2) commissioned systematic reviews (appendix pp 1–7), and (3) commissioned case studies."