Maternal stress during pregnancy is prevailing worldwide,which exposes fetuses to intrauterine hyper glucocorticoids (GC),programming offspring to obesity and metabolic diseases.Despite the importance of brown adipose tissue (BAT) in maintaining long-term metabolic health,impacts of prenatal hyper GC on postnatal BAT thermogenesis and underlying regulations remain poorly defined.Pregnant mice were administrated with synthetic GC dexamethasone (DEX) at levels comparable to fetal GC exposure of stressed mothers.Prenatal GC exposure dose-dependently reduced BAT thermogenic activity,contributing to lower body temperature and higher mortality of neonates;such difference was abolished under thermoneutrality,underscoring BAT deficiency was the major contributor to adverse changes in postnatal thermogenesis due to excessive GC.Prenatal GC exposure highly activated Redd1 expression and reduced Ppargc1a transcription from the alternative promoter (Ppargc1a-AP) in neonatal BAT.During brown adipocyte differentiation,ectopic Redd1 expression reduced Ppargc1a-AP expression and mitoehondrial biogenesis;and the inhibitory effects of GC on mitochondrial biogenesis and Ppargc1a-AP expression were blocked by Redd1 ablation.Redd1 reduced protein kinase A phosphorylation and suppressed cyclic adenosine monophosphate (cAMP)-responsive element-binding protein (CREB) binding to the cAMP regulatory element (CRE) in Ppargc1a-AP promoter,leading to Ppargc1a-AP inactivation,in summary,excessive maternal GC exposure during pregnancy dysregulates Redd1-Ppargc1a-AP axis,which impairs fetal BAT development,hampering postnatal thermogenic adaptation and metabolic health of offspring.