PROJECT SUMMARY Very preterm infant growth patterns are linked to neurodevelopmental and health outcomes, yet, ideal growth pattern trajectories have not been established as a means to guide nutritional intervention for this population. With the majority of very preterm infants exhibiting growth below the expected fetal or infant trajectory, greater characterization of very preterm infant growth is an essential step to elucidate the role of nutrition in the care and development of preterm infants. The overarching objective is to identify very preterm infant growth patterns prior to term age and across the first year of life that are phenotypically-defined (maternal, infant, and environmental factors including social determinants of health) and determine the impact of the phenotypically- informed growth patterns on very preterm infant neurodevelopmental and health outcomes. We hypothesize that phenotypic-derived latent class growth analysis-derived curves encompassing clinical and environmental exposures across the continuum of the neonatal intensive care unit (NICU) and post-discharge periods will identify growth patterns predictive of outcomes. To investigate this hypothesis, patterns of growth will be classified for two sentinel epochs spanning birth to 36 weeks' gestational age (the NICU period) and birth to 12 months' corrected age (infancy). Through a detailed collection of maternal and infant health, social and environmental determinants of health, nutrient intake, and body composition; the very preterm infant exposures differentially represented in these phenotypically-informed growth patterns will be identified. Subsequently, the impact of these phenotypically-informed growth patterns on neurodevelopmental and health outcomes will be determined. Lastly, a repository of longitudinally-collected biologic samples through the first two years of age will be established to foster a deeper exploration of the metabolic processes related to the identified phenotypes. This examination will be the first to bridge the NICU and post-hospital discharge epochs to investigate growth trajectory without predetermined expectations and informed by extensive nutrition, health, and social data. Through this investigation of phenotypically-defined growth patterns, the modifiable factors influencing growth trajectory and its link to very preterm infant outcomes will be revealed to inform both clinical care and future interventional trials to optimize nutrition and growth for each very preterm infant.