OBJECTIVES: To conduct a systematic review to examine the incremental benefits of mothers’ own milk (MM), with or without fortification, compared with donor milk (DM) and/or preterm formula (PF) for the nutritional support of preterm infants both in the neonatal intensive care unit (NICU) and following hospital discharge. METHODS: English-language studies published post-1990 were identified from electronic databases (Medline, EMBASE and Cochrane Library) and conference proceedings. Eligible studies enrolled infants with mean gestational age less than 35 weeks with no restriction on geographical location. RESULTS: Thirty-three unique studies met eligibility criteria: United States (n=12), Canada (n=2), Australia (n=2), Mexico (n=1), Israel (n=2), Europe (n=13) or multinational (n=1). There was a paucity of both RCT data (n=7) and studies which reported exclusive use of MM feeding (n=3). In addition, there was considerable heterogeneity between studies with regard to study design, duration of follow up and amounts of MM ingested, and a robust meta-analysis was therefore not feasible. However, a significant beneficial effect for MM over DM and/or PF for the incidence of sepsis, necrotizing enterocolitis (NEC) and longer-term neurodevelopment was reported in a number of individual studies. With regard to anthropomorphic outcomes of body weight, length and head circumference, there was no clear consensus on the effect of feeding regimen. Sixteen studies reported the relationship between the dose of MM received and outcomes;  increased MM dosages in the feeding regimen were associated with significantly lower rates of sepsis, NEC, and hospital readmissions, reduced  NICU costs, and improved neurodevelopment. CONCLUSIONS: Exclusive or high-dose MM with or without fortification is associated with short- and long-term beneficial effects in preterm infants. These results confirm MM to be the optimal nutrition for preterm infants and stress the importance of developing comprehensive strategies to overcome the challenges of providing MM and improving breastfeeding rates in preterm infants in the NICU.