a, Unsupervised hierarchical clustering of 753 maternal serum metabolites (n = 6 dams). b, Amino acid, lipid and xenobiotic metabolites dysregulated in E14.5 fetal brains of offspring from ABX vs. SPF dams (left) and ABX vs. Sp dams (right) (q<0.05; One-way ANOVA, n=6 embryos from different dams). c, Amino acid, lipid and xenobiotic metabolites significantly dysregulated in E14.5 fetal brains of offspring from GF dams vs. SPF controls (left) and GF dams vs. Sp dams (right) (q<0.05; One-way ANOVA, n=offspring from 6 dams per group). d, Random Forest classification of top 30 metabolites in maternal serum that discriminate between SPF and Sp vs. ABX and GF dams. (n=6 dams). e, Relative concentrations of N,N,N-trimethyl-5-aminovalerate (TMAV), trimethylamine N-oxide (TMAO), imidazole propionate (IP), hippurate (HIP), and 3-indoxyl-sulfate (3-IS) in maternal sera of SPF, ABX, GF, and Sp dams (One-way ANOVA with FDR contrasts; n=6 dams). Mean±SEM. *q<0.05, **q<0.01, ***q<0.001, ****q<0.0001, n.s.=not statistically significant.