Meconium Microbiome Maturation Patterns Linked to Postnatal Growth Failure in Neonates

Background/Objectives: This study investigated whether meconium microbial profiles differed according to postnatal growth failure (PGF) and whether gestational age (GA)-related microbial maturation patterns appeared to vary according to subsequent growth status. Methods: Meconium samples were collected from 310 neonates born at 22-40 weeks of gestation, and 16S rRNA sequencing was conducted. After excluding small-for-gestational-age infants, the analyses included 151 samples from PGF+ infants and 131 samples from PGF- infants. Microbial composition, alpha and beta diversity were compared according to PGF status. Distance-based redundancy analyses (dbRDA) were conducted to evaluate the independent association between PGF and microbiome composition. Results: The core meconium microbiome differed between groups. PGF+ infants showed a predominance of Proteobacteria (36.60% vs. 27.96%), whereas PGF- infants had relatively higher abundances of Firmicutes (35.47% vs. 30.64%) and Bacteroidetes (28.96% vs. 26.19%) than PGF+ infants. GA-related microbial maturation patterns also differed between groups. At the genus level, the PGF- group showed significant positive correlations with GA for Faecalibacterium, Sutterella, Dialister, Megamonas, Escherichia/Shigella, and Roseburia after false discovery rate correction, whereas no genus-level correlation remained significant in the PGF+ group. Alpha diversity did not differ significantly between groups, whereas beta diversity differed modestly (R² = 0.0087, p = 0.042). After adjustment for GA and birth weight, the PGF effect remained significant in the Bray-Curtis-based dbRDA model, whereas it was not significant in the Jaccard-based model. Conclusions: PGF was associated with abundance-based shifts within shared meconium taxa, suggesting subtle differences in early microbial developmental patterns among infants who later developed PGF.