Routine Iron Supplementation on the Neonatal Gut Microbiome

The gastrointestinal microbiome in preterm infants exhibits significant influence on optimal outcomes - with dysbiosis shown to substantially increase the risk of the life-threatening necrotizing enterocolitis and additional impaired outcomes. Iron is a vital nutrient especially during the perinatal window of rapid hemoglobin production, tissue growth, and foundational neurodevelopment. However, excess colonic iron exhibits potent oxidation capacity and alters the gut microbiome - potentially facilitating the proliferation of pathological bacterial strains. Human milk-fed preterm infants routinely receive iron supplementation after delivery and are highly vulnerable to morbidities associated with gastrointestinal dysbiosis. Therefore, we set out to determine if routine iron supplementation alters the preterm gut microbiome. After IRB approval, we collected stool specimens from 14 infants born less than 34 weeks gestation in the first, second, and fourth week of life to assess gut microbiome composition via 16S rRNA sequencing. We observed no significant differences in either phyla or key genera relative abundance between pre- and post-iron timepoints. We observed notable shifts in infant microbiome composition based on season of delivery. Though no obvious indication of iron-induced dysbiosis was observed in this unique study in the setting of prematurity, further investigation in a larger sample is warranted to fully understand iron's impact on the gastrointestinal milieu.