Probiotic treatment rescues behavioral deficits and gut microbial abnormalities induced by preconceptional stress in mothers and offspring

• Preconception stress alters maternal microbiota and induces anxiety-like behavior. • Probiotic supplementation normalizes stress-related microbial and behavioral changes. • Maternal microbial alterations are transmitted to offspring gut communities. • Probiotic exposure rescues offspring anxiety and cognitive deficits in a sex-dependent manner. • Probiotics emerge as a promising intervention for stress-related perinatal dysregulation. Depression and anxiety during pregnancy are major public health concerns with lasting consequences for mother and child. Although the gut microbiome contributes to stress and mood regulation, its role in preconceptional stress and transgenerational outcomes remains unclear. Here, we examined behavioral, microbial, and thalamic transcriptional effects of preconceptional social isolation rearing (SIR) in female mice and tested whether maternal probiotic supplementation mitigates these alterations. SIR females displayed increased anxiety-like and social-avoidant behavior, reduced gut microbial diversity, depletion of Odoribacter, Tuzzerella, and Alloprevotella, and enrichment of Bacteroides and Lachnospiraceae. A multispecies probiotic (Lactobacillus rhamnosus HN001, L. acidophilus La-14, Bifidobacterium lactis HN019) reversed these behavioral and microbial changes. Adult offspring of SIR dams showed sex-dependent behavioral deficits and microbial alterations partly reflecting maternal patterns. Prenatal SIR was associated with reduced thalamic Bdnf expression in offspring and altered Grin2a/2b selectively in males. In contrast, prenatal probiotic exposure exerted broader transcriptional effects and restored Bdnf levels in SIR offspring. SIR-induced increases in Lachnospiraceae were transmitted to offspring, whereas reductions in Ruminococcaceae were normalized by maternal probiotic treatment. Predicted functional profiling indicated sex-dependent modulation of microbial pathways related to tryptophan and central carbon metabolism. These findings demonstrate enduring transgenerational effects of preconceptional stress on the gut–brain axis and support maternal probiotic supplementation as a potential strategy to mitigate stress-induced dysregulation.