Targeted Fortification of Donor Breast Milk in Preterm Infants

The control group will receive mother's breast milk when it is available. Mother's breast milk will be fortified with 4 packets of Similac Human Milk Fortifier (HMF) per 100 mL. When mother's breast milk is not available, participants will be fed donor breast milk with 4 packets of HMF.

For participants in the control group, additional fortification can be added to the milk for patients in this group in response to poor growth, as is standard of care in the NICU. The standard dose is 1 ml per 30 ml of breast milk.

For participants in the control group, additional fortification can be added to the milk for patients in this group in response to poor growth, as is standard of care in the NICU. The standard dose is 1 ml per 30 ml of breast milk.

For participants in the control group, additional fortification can be added to the milk for patients in this group in response to poor growth, as is standard of care in the NICU.

The experimental group will receive mother's breast milk when it is available. Mother's breast milk will be fortified with 4 packets of Similac Human Milk Fortifier (HMF) per 100 mL. When mother's breast milk is not available, participants will be fed donor breast milk with 4 packets of HMF. For participants in the experimental group, the investigators will continue to add fortification. Two packets of HMF per day will be added until goal fortification is reached.

Participants in the experimental group will receive a dose that will vary depending on the base protein content in the donor breast milk for each particular batch of donor breast milk.

Participants in the experimental group will receive a dose that will vary depending on the base fat content in the donor breast milk for each particular batch of donor breast milk

Participants in the experimental group will receive a dose that will vary depending on the base carbohydrate content in the donor breast milk for each particular batch of donor breast milk

For participants in both the control and the experimental arms, each batch of donor milk will be analyzed using the Miris Human Milk Analyzer. Manufacturer recommendations for milk analysis will be strictly followed.