PROJECT SUMMARY/ABSTRACT Newborn health has improved in the United States in recent decades yet still lags that of other high-income countries. A critically important yet understudied reason for this disappointing gap is the nature of the inpatient care received by newborns and the effects this has on health during the first year of life. Neonatal care and outcomes have been shown to vary markedly from hospital to hospital and between neonatal intensive care units (NICUs), yet little is known about the causes and consequences of this variation, particularly for lower-risk (e.g., less premature) newborns, who occupy most NICU beds today; few studies have examined how widely differing patterns of care are linked to post-discharge outcomes. Our long-term goal is to extend our previous descriptive studies of newborn-care variation to investigate and identify the temporal sequence of risk, medical care, and outcomes through the first year of life. We will do so using a population-based cohort of 1.13 million Medicaid-insured Texas newborns (54% of Texas births, 1 in 18 of US births). This unique dataset, developed by members of our team, links maternal and newborn Medicaid claims/encounters to natality and mortality records. Our central hypothesis is that newborn care, and subsequent infant health outcomes, are strongly associated with specific, modifiable aspects of newborn and post-discharge care. We will study five gestational age singleton cohorts: (1) very preterm, (2) moderately preterm, (3) early preterm, (4) early term, and (5) term. In Aim 1, we will investigate the association of neonatal hospital care with hospital characteristics. We will then test the association of these care patterns with mortality and morbidity (severe conditions, readmissions, and ER use) during the inpatient period plus 7 days post-discharge. In Aim 2, the observation period is extended to one-year post-discharge, with additional outcomes such as infant diagnoses derived from claims and multiple weight measurements obtained from the Women, Infants, and Children Nutritional Program. We will test associations of these risk-adjusted outcomes with birth-hospital characteristics, neonatal care, and post- neonatal care. In Aim 3, we investigate the possible amplifying effects of hospital-level maternal race and ethnicity composition on the foregoing analyses. This project will significantly advance our knowledge of newborn care and outcomes for a large, diverse total birth cohort through the first year of life, providing detailed information about determinants of early health. The findings will create actionable opportunities to improve perinatal care delivery through policy development and new clinical improvement initiatives.