Human-derived Human Milk Fortifiers (H2MF), Gut Microbiota and Oxidative Stress in Premature Infants

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…