The first 1000 days: the price of inequalities in high and middle-income countries.

The first 1000 days of human life start from conception until the child turns 2 years of age. This is a unique period in which the foundations of a child's lifelong health are built. Disadvantaged socioeconomic circumstances and limited access to health care services can globally affect a child's health outcomes and educational and vocational potential. This article discusses health inequalities over the first 1000 days of life and possible mitigation programs. Governments and politicians should promote fairer health interventions and pediatric healthcare workers should be aware of the main health determinants to advocate for more equitable and child-focused resource allocation. Therefore, the main approaches to contrast health inequalities include cooperation between governments and public health professionals, removing barriers to accessing medical care, and raising staff awareness about health determinants. Finally, pro-equality interventions should include providing services commensurate with the level of need, in adherence to the principle of social justice. IMPACT: This review aims to elicit a detailed understanding of how inequalities affect early childhood development in different socio-economic contexts, focusing on both the short and long-term consequences. The greatest impact comes precisely from providing valuable tools for both clinicians and public health practitioners to understand and read, in daily practice, the effects produced by health determinants and health inequalities.