O'Connor 2018.

Methods	Randomized clinical trial
Participants	127 infants < 1250 g Exclusion criteria: Receipt of formula or bovine milk‐based fortifier prior to randomization and if enteral feeding not commenced within 14 days after birth. Congenital or chromosomal anomaly affecting growth. Setting: 2 tertiary NICUs, Sinai Health System and The Hospital for Sick Children, Toronto, Canada.
Interventions	Intervention: (N = 64) Mother's own milk or pasteurized donor human milk fortified with human milk‐based fortifier (HMBF) (Prolact+, Prolacta Bioscience) to achieve 0.81 kcal/mL (24 kcal/oz), and 0.88 kcal/mL (26 kcal/oz), Control: (N = 63) Mother's own milk or pasteurized donor human milk fortified with bovine milk‐based fortifier (BMBF) (Similac Human Milk Fortifier Powder, Abbott Nutrition) to 0.72 kcal/mL (22 kcal/oz) and 0.78 kcal/mL (24 kcal/oz), and with the addition of powdered formula (Similac Neosure, Abbott Nutrition) to further concentrate feeds to 0.88 kcal/mL (26 kcal/oz).
Outcomes	Interruption in enteral feeding unrelated to clinical procedure ≥ 12 hours or a > 50% reduction in feed volume Days of parenteral nutrition Growth Dichotomous mortality and morbidity index including NEC Stage ≥ 2, chronic lung disease, severe retinopathy of prematurity, and late‐onset sepsis Fecal calprotectin
Notes	Fortification of breast milk in both groups commenced at feed volumes of ≥ 100 mL/kg/d. In the HMBF group, fortification began at 0.81 kcal/mL (24 kcal/oz), and increased to 0.88 kcal/mL (26 kcal/oz) when volume reached 140 mL/kg/d. In the BMBF group, fortification began at 0.72 kcal/mL (22 kcal/oz) and increased to 0.78 kcal/mL (24 kcal/oz) when volumes reached 140 mL/kg/d. In the BMBF group, intact‐protein modular (Beneprotein, Nestle) was added to donor milk after fortification had reached up to 0.78 kcal/mL)
Risk of bias
Bias	Authors' judgement	Support for judgement
Random sequence generation (selection bias)	Low risk	Block randomization of 4
Allocation concealment (selection bias)	Low risk	Allocation by an online third party service
Blinding of participants and personnel (performance bias) All outcomes	Low risk	Triple‐blind study. Feeding assignments were masked using amber colored tubing and color wrapping for bottles.
Blinding of outcome assessment (detection bias) Self‐reported outcomes	Low risk	Triple‐blind study. The reporting team was blinded to the intervention.
Blinding of outcome assessment (detection bias) Objective outcomes	Low risk	Triple blind‐study. The reporting team was blinded to the intervention.
Incomplete outcome data (attrition bias) All outcomes	Low risk	Two infants (2/63) in the control group were excluded since they died before intervention.
Selective reporting (reporting bias)	Low risk	All outcomes planned were reported.
Other bias	Low risk	None noted

BMBF: Bovine milk‐derived fortifier
 HMBF: Human milk‐derived fortifier
 NEC: Necrotizing enterocolitis
 NICU: Neonatal intensive care unit