The objective of the study is to compare two human milk fortifiers with different protein content and LCPUFA in a group of very low birth weight infants.

This study is a multi-center, third party-blinded, randomized, controlled, parallel- group, prospective trial comparing growth with a liquid human milk fortifier with higher protein content and LCPUFA and a control powdered human milk fortifier added to breast milk and fed to premature infants. The trial will be conducted in 11 centers in Chile. The enrollment period is expected to be approximately 18 months. To allow for dropouts, approximately 160 participants will be randomized.

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