Individualized Fortification of Breast Milk (IFO)

Inclusion criteria:

1. Gestational age < 32weeks (maternal dates or early fetal ultrasound);
2. Tolerating an enteral intake of ≥ 100 ml/kg/d for ≥ 24h;
3. Subject is anticipated to receive the intervention for ≥ 3 consecutive weeks after full enteral feeding (≥ 150 mL/kg/d) has been achieved; and
4. Written informed consent has been obtained from the infant's legal representative.

Exclusion criteria:

1. Infants with intrauterine growth restriction, small for gestational age defined by a weight less than 3rd percentile using sex specific reference data for birth weight
2. Gastrointestinal malformation, major congenital anomalies and chromosomal abnormalities;
3. Babies with enterostoma or short gut syndrome;
4. Necrotizing enterocolitis, defined by feeding intolerance associated with positive x-ray findings (pneumatosis intestinalis - Bell Stage 2; air in the biliary tract or free air in the peritoneum - Bell Stage 3);
5. Renal disease, defined by symptoms (oliguria, anuria, proteinuria, hematuria) associated with an increased blood urea nitrogen 10 mmol/L79 and creatinine of 130 mmol/L80;
6. Hepatic dysfunction, defined by jaundice (direct bilirubin >1.0 mg/dl) that is associated with one or more abnormal liver function tests (AST, ALT or GGT);
7. Participation in another clinical trial that may affect outcomes of this study; or
8. Probability of transfer to another NICU or level II nursery outside the McMaster Children's Hospital before the minimum period of three weeks is completed.

Post-randomisation exclusion criteria:

1. Infants fed more than 25% of mean caloric intake for a consecutive week with formula milk;
2. Fluid restriction < 140mL/kg/d for ≥ 3 consecutive days;
3. Sepsis - all infants with gram-negative sepsis will be removed from the study.