This is a randomized controlled trial of a human-derived human milk fortifier (H2MF) vs standard bovine-derived human milk fortifier (HMF) evaluating fecal microbiota and fecal and urinary biomarkers of oxidative stress in premature infants.

While breast milk provides complete nutrition for full term infants, supplementation with human milk fortifiers (HMF) is required to achieve optimal weight gain in very low birthweight (VLBW) preterm neonates. Traditionally, HMF have been derived from bovine milk. Bovine-based infant formula has been shown to cause dysbiosis of the infant gut microbiome (Azad et al 2013) and increased oxidative stress in preterm neonates (Friel et al 2011). Microbiome dysbiosis and oxidative stress have been implicated in numerous inflammatory conditions, including both acute (eg. necrotizing enterocolitis, NEC) and long-term (eg. asthma, metabolic syndrome) sequela of preterm birth (Torrazza et al 2013, Goulet et al 2015, Flora et al 2007, Perrone et al 2014). Recent studies show that new human-derived HMF (H2MF) are superior to standard bovine HMF for nourishing VLBW preterm infants and preventing NEC (Sullivan et al 2010, Cristofalo et al 2013). However, the biological basis for these clinical benefits is unknown, which limits our ability to inform and improve feeding strategies for VLBW preterm infants. This will be the first study to evaluate the impact of H2MF on gut microbiota and oxidative stress in preterm infants.

Specific Objectives:

1. To evaluate the effect of H2MF vs. HMF on gut microbiota composition in premature infants born <1250 gr between 26 and 30 weeks of gestational age.
2. To evaluate the effect of H2MF vs. HMF on fecal and urinary biomarkers of oxidative stress in premature infants born <1250 gr between 26 and 30 weeks of gestational age.

Inclusion Criteria:

• Male or female infant with birth weight <1250 grams
• Gestational age between 26+0 to 30+0 weeks at birth
• Able to adhere to feeding protocol
• Parenteral nutrition must be started by day of life 2
• Enteral feeding >80 ml/kg/d should be reached by day of life 14
• Subject's parent(s)/legal guardian(s) has provided signed and dated informed consent and authorization to use protected health information, as required by national and local regulations.
• In the investigator's opinion, the subject's parent(s)/legal guardian(s) understands and is able to comply with protocol requirements, instructions, and protocol-stated restrictions, and is likely to complete the study as planned.

Exclusion Criteria:

• Gestational age > 30+0 weeks at birth (to guarantee a minimum of 3 weeks H2MF treatment, since fortification ends at 33+0 AGA)
• Gestational age < 26+0 weeks at birth (to minimize baseline heterogeneity, since gestational age influences gut microbiota)
• Received antibiotics on the first day of specimen collection (to minimize baseline heterogeneity, since antibiotics influence gut microbiota) Note: all infants are expected to receive up to 48 hr antibiotic prophylaxis at birth according to standard NICU protocol; this criterion will exclude infants receiving extended courses of antibiotics.
• Received probiotics at any time (to minimize baseline heterogeneity, since probiotics influence gut microbiota)
• Unlikely to survive the study period
• Presence of clinically significant congenital heart disease or other major congenital malformation
• Presence prior to enrollment of intestinal perforation or stage 2 necrotizing enterocolitis (NEC) prior to tolerating fortified feeds

At this time we plan to share IPD within our research team only. We will consider sharing with other researchers in the future.

Masking of care providers is not feasible since the procedures of preparation for HMF and H2MF are different. Outcome assessors (personnel analyzing microbiome profiles and oxidative stress biomarkers) will be masked.