Orlandi, Amy

AbstractBackgroundInfants born via Cesarean section (C‐section) often have a distinct gut microbiome and higher risks of atopic and immune‐related conditions than vaginally delivered infants. We evaluated whether a microbiome‐based program could shift gut microbiome composition and improve microbiome‐associated health outcomes in C‐section born infants.MethodsThis open‐label, randomized, controlled trial included full‐term C‐section‐born infants aged 0–3 months, randomized to an intervention (n = 25) or control arm (n = 29). Over 6 months, the intervention arm received two microbiome reports, personalized recommendations based on their microbiome, educational materials, and coaching calls focused on microbiome health. Parents reported health conditions via surveys. Primary outcome: Difference between study arms in relative abundance of key gut microbiome taxa and functional genes. Other outcomes: Changes in a C‐section index—a taxonomy‐based metric comparing C‐section‐associated taxa to vaginally‐associated taxa—and prevalence of atopic conditions.ResultsCompared to controls, the intervention arm had higher Bifidobacterium (p = .025, q = .121) and higher abundance of genes associated with human milk oligosaccharide degradation (e.g., α‐L‐fucosidase, p = .019, q = .046) at timepoint 2. In the intervention arm, the C‐section index decreased to a level similar to vaginally born infants (p = .807, q = .807). At the end of the intervention, atopic dermatitis prevalence was lower in the intervention arm than in controls (odds ratio, 0.17 [95% CI, 0.023–0.723], p = .031).ConclusionA personalized microbiome‐based program can modulate the gut microbiome of C‐section‐born infants and may reduce the risk of atopic conditions (ClinicalTrials.gov: NCT06424691).