Intergenerational disruptions to reproductive, physical, and neurobehavioral development in rats after prenatal exposure to the emergent pollutant betamethasone.

Betamethasone (BM) is the standard clinical treatment for accelerating fetal lung maturation in women at risk of preterm delivery. However, emerging evidence identifies BM as posing a significant "One Health" challenge. While antenatal corticosteroid therapy provides immediate neonatal benefits, early overexposure to glucocorticoids is linked to fetal programming and the Developmental Origins of Health and Disease (DOHaD), with potential consequences spanning multiple generations. The aim of this work was to evaluate the impacts of prenatal BM exposure on physical, neurobehavioral, and reproductive initial developments of F1 offspring and subsequent F2 (offspring of F1 male rats) and F2' (offspring of F1 female rats). For this, pregnant dams (F0) received intramuscular injections of BM (0.1 mg/kg) or saline during the critical window of genital system development (gestational days 12, 13, 18, and 19). Developmental landmarks, puberty onset, and reproductive parameters were monitored across generations. Prenatal BM exposure reduced maternal body weight gain and lowered F1 birth weight, which was followed by subsequent "catch-up" growth. In F1 females, BM significantly delayed puberty onset and deregulated the estrous cycle. In F1 males, absolute testicular weight was reduced, and sperm quality was significantly impaired. Physical and neurobehavioral milestones (e.g., incisor eruption, eye opening, and negative geotaxis) were delayed across the F1 and F2 generations. Notably, anogenital distance (AGD) was increased in F2' females, indicating a masculinized phenotype and HPG axis programming. These translational findings demonstrate that intrauterine BM overexposure induces intergenerational toxicity, persisting in not directly treated offspring through developmental programming. Given the widespread clinical use of BM and the environmental persistence of synthetic glucocorticoids, these results reinforce the need to assess the long-term safety of clinical interventions and the latent ecological risks of these potent steroid compounds.