The purpose of this study is to assess growth of preterm infants fed human milk supplemented with an experimental human milk fortifier.

Inclusion Criteria:

• 700-1500g birth weight
• 33 weeks or less gestational age
• Appropriate for gestational age
• Initiate enteral feeds of human milk by 21 days of life
• Mother provided exclusive human milk feeds
• Parents allow both human milk and study human milk fortifier
• Singleton or twin birth

Exclusion Criteria:

• Feeding preterm infant formula or non-study human milk fortifier
• Expected at facility less than 15 days
• Congenital anomalies/disease affecting growth and development
• 5 minute APGAR of 4 or less
• Steroid use
• ECMO
• Grade III or IV PVH/IVH
• Mechanical ventilator dependency
• Maternal incapacity
• History of major surgery
• Asphyxia
• Confirmed NEC or sepsis
• Use of probiotics