The challenge of the first 1000 days. The dynamics of early-life health inequalities in a universal healthcare system: Evidence from Italy

Research in Context: (1) What is already known about the topic? Low birth weight (LBW) is a key marker of early-life health disadvantage, associated with increased mortality, delayed development, and long-term socioeconomic challenges. Health disparities related to LBW are predictive of future health outcomes and life trajectories. Although universal healthcare systems can mitigate such inequalities, their effectiveness varies across health domains and population subgroups. (2) What does this study add to the literature? This study examines how LBW-related health disparities evolve during early childhood within the universal healthcare system of Lombardy, Italy. Using robust statistical approaches, including twin fixed-effect models, the study shows that initial disadvantages in hospitalization rates and severity substantially decrease within the first 1000 days of life, particularly for nervous and digestive system conditions. However, disparities persist in respiratory diseases, indicating uneven mitigation across health domains. The study contributes new evidence on how universal healthcare can promote health equity in early life, while highlighting residual areas of concern. (3) What are the policy implications? The findings suggest that universal healthcare systems can significantly reduce health inequalities linked to LBW, but targeted interventions are necessary to address persistent disparities-especially in respiratory health. Policymakers should consider strengthening prenatal and neonatal care and designing condition-specific strategies that extend beyond infancy. Tailored support for LBW infants can further improve long-term outcomes and enhance the overall effectiveness of universal healthcare in promoting equitable health. Background: Early-life health inequalities can shape long-term health outcomes. This study examines disparities in hospitalization rates and severity between low-and normal-birth-weight children aged 0-3 years in Lombardy, Italy, under a universal public healthcare system. Objective: To analyze the evolution of early-life health inequalities in hospitalization rates and severity between low-and normal-birth-weight children. Methods: A retrospective longitudinal study leveraging a unique administrative dataset that integrates birth records and hospital discharge data for a large cohort of children in Lombardy. This approach allows for a robust analysis of hospitalization probabilities, total reimbursement costs, and hospital length of stay over the critical first 1000 days of life. Subgroup analyses focus on nervous, digestive, and respiratory diseases. Twin birth data are used to strengthen causal inference. Results: Low-birth-weight children experience higher hospitalization rates and greater severity in the first year of life, but disparities substantially decline over time, with no significant differences in costs or hospital stays after 1000 days. While inequalities decrease most for nervous and digestive system diseases, they persist for respiratory conditions. Findings are consistent in twin analyses, reinforcing the study's robustness. Conclusion: By leveraging rich administrative data and a longitudinal framework, this study highlights the capacity of a universal healthcare system to mitigate early-life health disparities, particularly for nervous and digestive conditions. However, persistent respiratory disparities call for targeted interventions. These insights can inform future policies aimed at enhancing health equity from birth.