Investigators hypothesize that in infants \< 32 completed weeks of gestation, combined treatment with Darbe plus FMX or Darbe plus LMW-ID will: 1) be safe, 2) decrease or eliminate transfusions, 3) maintain iron sufficiency, 4) result in higher hematocrit and 5) improve neurodevelopment. Investigators further hypothesize that when compared to oral iron supplementation (standard care), IV iron will be better tolerated, with less effect on the gastrointestinal (GI) microbiome
Objectives:
1. To compare the safety, dose, and dosing interval for FMX and LMW-ID required for preterm infants receiving Darbe.
Iron dosing will begin at 7 days after birth. Initial doses of 10 mg/kg/dose or 20 mg/kg/dose will be compared for each iron formulation (N=20 each).
2. To compare the safety, tolerance, and efficacy of IV iron (FMX or LMW-ID) plus Darbe (N=80) to standard care (oral ferrous sulfate (N=40). Adverse reactions to IV Iron will be documented, as will adverse responses to oral iron (feeding intolerance). Potential differences in the stool microbiome will be evaluated 3 weeks after the initial IV and oral iron doses.
3. Determine long-term outcomes:
* 3.1 Neurodevelopmental outcomes of infants enrolled in Objectives 1 and 2 (N=120) will be sequentially assessed up to 2 years of age.
* 3.2 The stool microbiome will be compared between study groups at 12 and 24 months to determine whether mode of iron delivery has long-term effects.
