Our Series on optimising child and adolescent health and development follows on almost two decades after the original Lancet Series on child survival and its corresponding call for action. 1 The Bellagio Study group on Child SurvivalKnowledge into action for child survival. Lancet. 2003; 362: 323-327 Summary Full Text Full Text PDF PubMed Scopus (184) Google Scholar With less than 10 years left to meet the 2030 Sustainable Development Goals (SDGs), we are concerned that, once again, the world is failing its children. The evidence is strong and calls for change abound; however, effective actions are few and far between. Opportunities in crisis for optimising child health and developmentThe Lancet Series on optimising child and adolescent health and development1–4 arrives at the right time. For many years, the global health community has known that quality primary health care, including antenatal care, immunisation, and optimal nutrition, helps children survive past their fifth birthday and live healthy lives. Child survival has improved because of combined efforts in these areas; but the scale and scope of the global threats to child health and wellbeing, including conflicts, climate crises, and other humanitarian emergencies, all compounded by COVID-19, now put decades of progress at grave risk. Full-Text PDF Health and development from preconception to 20 years of age and human capitalOptimal health and development from preconception to adulthood are crucial for human flourishing and the formation of human capital. The Nurturing Care Framework, as adapted to age 20 years, conceptualises the major influences during periods of development from preconception, through pregnancy, childhood, and adolescence that affect human capital. In addition to mortality in children younger than 5 years, stillbirths and deaths in 5–19-year-olds are important to consider. The global rate of mortality in individuals younger than 20 years has declined substantially since 2000, yet in 2019 an estimated 8·6 million deaths occurred between 28 weeks of gestation and 20 years of age, with more than half of deaths, including stillbirths, occurring before 28 days of age. Full-Text PDF Effects of early-life poverty on health and human capital in children and adolescents: analyses of national surveys and birth cohort studies in LMICsThe survival and nutrition of children and, to a lesser extent, adolescents have improved substantially in the past two decades. Improvements have been linked to the delivery of effective biomedical, behavioural, and environmental interventions; however, large disparities exist between and within countries. Using data from 95 national surveys in low-income and middle-income countries (LMICs), we analyse how strongly the health, nutrition, and cognitive development of children and adolescents are related to early-life poverty. Full-Text PDF What can work and how? An overview of evidence-based interventions and delivery strategies to support health and human development from before conception to 20 yearsProgress has been made globally in improving the coverage of key maternal, newborn, and early childhood interventions in low-income and middle-income countries, which has contributed to a decrease in child mortality and morbidity. However, inequities remain, and many children and adolescents are still not covered by life-saving and nurturing care interventions, despite their relatively low costs and high cost-effectiveness. This Series paper builds on a large body of work from the past two decades on evidence-based interventions and packages of care for survival, strategies for delivery, and platforms to reach the most vulnerable. Full-Text PDF Improving health and social systems for all children in LMICs: structural innovations to deliver high-quality servicesDespite health gains over the past 30 years, children and adolescents are not reaching their health potential in many low-income and middle-income countries (LMICs). In addition to health systems, social systems, such as schools, communities, families, and digital platforms, can be used to promote health. We did a targeted literature review of how well health and social systems are meeting the needs of children in LMICs using the framework of The Lancet Global Health Commission on high-quality health systems and we reviewed evidence for structural reforms in health and social sectors. Full-Text PDF