Objective: The aim of the study was to investigate the impact of intrapartum antibiotic treatment (IAT) on the compositional development of gut microbiota in healthy term infants.

Study design: A case-control study of 24 infants exposed to and 24 matched infants not exposed to IAT was conducted. All subjects were born by vaginal delivery at term and breastfed. None of the infants received antibiotics during the immediate neonatal period. Fecal samples were obtained at the ages of 1 and 6 months. The composition of the intestinal microbiota was assessed by 16S rRNA gene sequencing.

Results: IAT was associated with reduced microbial richness but not diversity at 1 month of age. Furthermore, the relative abundances of Clostridiaceae and Erysipelotrichaceae were significantly altered in infants exposed to IAT as compared to nonexposed infants at 1 month of age. The observed deviations in gut microbiota composition between infants exposed and not exposed to IAT diminished by the age of 6 months.

Conclusions: IAT is associated with short-term perturbations in the gut microbiota development in healthy term, vaginally delivered, breastfed infants. The composition of the gut microbiota is mostly restored by the age of 6 months.