Nutrition of Premature Infants With Human Breastmilk Fortifier

Inclusion Criteria: * Premature infant equal or under 31 weeks gestational age at birth * Birth weight equal or under 1,250 g * Predominantly fed breast milk (mother's milk or donor milk) on study day 0 * Appropriate birth weight for gestational age (AGA) - defined as birth weight between and inclusive of the 10th and 90th percentiles on the Fenton growth chart * Singleton or twin birth (both twins do not need to qualify and be randomized into study) * Birth weight is ≤1,000 g and participant is ≤ 40 days of age on study day 0 * Birth weight is above 1,000 g and participant is ≤ 30 days of age on study day 0 * Enteral intake of 80 mL/kg/d of unfortified breast milk on study day 0 * Anticipate mother's willingness to breast milk for at least 28 days from study day 0 * Signed informed consent obtained Exclusion Criteria: * History of underlying metabolic or chronic disease, congenital malformation, or any other condition which, in the opinion of the Investigator, is likely to interfere with: the ability of the participant to ingest food, normal growth and development of the participant, or the evaluation of the participant * 5 minute APGAR score ≤ 4 * Major surgery that required general anesthesia prior to first day study (note: persistent ductus arterious ligation is allowed) * Received pharmacologic doses of glucocorticoids during 3 consecutive days (72 hours) prior to or on day one of study (physiologic hydrocortisone administration up to 1.5 mg/kg/d is permitted) * Ventilator-dependent and requiring ≥ 40% fraction of inspired oxygen (FiO2) on day one of study (ventilator dependent and requiring ≤ 40% FiO2 and/or nasal canula, and/or nasal continous positive airway pressure (CPAP) and/or oxygen hood is allowed) * Grade III or IV bilateral intraventricular hemorrhage (IVH) prior to or on study day one * Feeding intolerance to breast milk feedings on study day one * Consumption of more than 3 feedings or 12 hours of continuous feeds of fortified breast milk prior to study day one * Fluid restriction \< 120 mL/kg/d * History of creatinine \>2.0 mg/dL 7 days prior to or on study day one * Currently receiving or plan use of probiotics