Prenatal exposure to glucocorticoids is linked to long-term health risks in offspring, but the role of maternal gut microbiota in mediating these effects remains unclear. Here, we demonstrate that prenatal prednisone therapy (PPT) in humans and prenatal prednisone exposure (PPE) in rats result in sex-specific long bone dysplasia in offspring, including reduced peak bone mass (PBM) and heightened osteoporosis risk in female offspring. Multi-omics profiling and fecal microbiota transplantation show that PPE alters maternal gut microbiota composition and depletes the microbial metabolite daidzein (DAI). DAI deficiency suppresses Hoxd12 expression, impairs osteogenesis, and leads to PBM decline in female offspring. In bone marrow-derived mesenchymal stem cells from PPE female offspring, DAI promoted Hoxd12 expression and osteogenic differentiation. Notably, DAI supplementation restored H3K9ac levels, enhanced Hoxd12 expression, and promoted osteogenic differentiation through the ERβ/KAT6A pathway. Furthermore, maternal DAI supplementation during pregnancy prevented osteoporosis susceptibility in PPE female offspring and alleviated functional abnormalities in multiple organs, including the liver, hippocampus, ovary, and adrenal gland. In conclusion, PPE induces multiorgan dysplasia and increases disease predisposition (e.g., osteoporosis) in female offspring by disrupting maternal gut microbiota and depleting DAI. Maternal DAI supplementation provides a promising preventive strategy to counteract these adverse outcomes.