['To investigate the effect of hCG on the expression of genes involved in oxidative stress resistance observed in decidualizing human endometrial stromal cells (HESCs).', 'In vitro experiment.', 'Saitama Medical University hospital.', 'Premenopausal women undergoing hysterectomy for myoma uteri.', 'HESCs from hysterectomy specimens were isolated and incubated with 8-bromo-cyclic adenosine monophosphate and medroxyprogesterone acetate in the presence or absence of recombinant hCG (rhCG) at various concentrations. Hydrogen peroxide was used as the source of reactive oxygen species (ROS).', 'Apoptotic cells, FOXO1, superoxide dismutase 2 (SOD2), Bax, and Bcl-2 protein expression.', 'In a dose-dependent manner, rhCG conferred additional protection to decidualizing HESCs against oxidative stress-induced apoptosis. In parallel, rhCG augmented the expression of the forkhead transcription factor FOXO1 and its downstream target, the ROS scavenger SOD2. rhCG also inhibited the expression of the proapoptotic Bax protein and up-regulated antiapoptotic Bcl-2 levels in decidualizing HESCs exposed to ROS.'] Does human chorionic gonadotropin confer resistance to oxidative stress-induced apoptosis in decidualizing human endometrial stromal cells?