Project Summary Globally, almost 15 million infants are born prematurely each year, disproportionately affecting low and middle- income countries. In the absence of mother?s milk (MOM), the World Health Organization and the American Academy of Pediatrics recommend using donor human milk (DHM) due to its protective effect against necrotizing enterocolitis, a life-threatening intestinal infection. In response to these recommendations, development of donor milk banks and the use of DHM is increasing globally, with many low and middle-income countries integrating donor milk banks into their public health strategies to reduce neonatal mortality. It is estimated that 800,000 infants globally receive DHM each year, yet very little is known about the nutritional composition of DHM; how composition is influenced by milk banking practices; and whether preterm nutrient recommendations are achieved when DHM is used with commercially available fortifiers. There is evidence that preterm infants fed DHM have inferior growth rates compared to infants receiving preterm formula or mother?s milk, even when multi-nutrient fortifiers are used, suggesting suboptimal nutritional support (macronutrients, micronutrients, or both). To develop effective nutritional therapies for the increasing number of preterm infants globally receiving DHM, evidence-based nutritional standards for DHM are urgently needed. Studies to-date on DHM composition have typically been small (< 50 samples) and represented milk from a single milk bank in a high-income setting, which may be different from DHM from milk banks in low-income settings. Additional limitations include the dearth of studies on vitamins, minerals, and bioactive factors, and the use methods that may overstate protein and lactose values. This proposal seeks to address these research gaps in global preterm infant nutrition by conducting a multi-site study with eight geographically diverse milk bank partners in high, middle, and low-income settings. We will examine and compare a broad range of nutrients in milk from 600 approved milk bank donors around the world to create comprehensive, geographically diverse nutrient profiles for DHM (Aim 1). Milk bank-level practices for pooling donors will be evaluated using simulation to identify effective strategies that can be used by milk banks to create more consistent nutrient profiles in DHM (Aim 2). Finally, we will evaluate whether currently available commercial fortifiers meet nutrient recommendations when used with DHM and will identify nutrients to enhance in the development of a DHM-specific fortifiers (Aim 3). The long-term goal of this study, designed in response to RFA-HD-21-006, is to improve preterm nutritional care globally for the growing number of infants who receive donor human milk.