Perinatal ampicillin exposure alters murine maternal fecal bile acid and acylcarnitine profiles

species. These microbial shifts coincided with substantial and reproducible metabolic remodeling, including elevated fecal acylcarnitines and altered bile acid profiles. Notably, we identified two previously uncharacterized trihydroxylated bile acids conjugated to a hexose moiety, which we annotated as cholic acid-galactose and taurocholic acid-galactose and synthesized. These metabolites were consistently associated with antibiotic exposure across public metabolomics data repositories. Finally, alterations in the maternal fecal microbiome and metabolome were associated with increased weight gain in offspring, suggesting potential pathways by which maternal antibiotic exposure may influence early developmental outcomes. These findings highlight microbial and metabolic signatures linked to perinatal antibiotic use and underscore the need to balance infection control with long-term infant health considerations.