OBJECTIVE There are abundant hematopoietic stem cells (HSCs) in cord blood. It is known that HSCs continue to differentiate to CLP, CMP and erythroid progenitor cells (EPC), EPC ultimately differentiated to platelets and erythrocytes. It has been reported that the proportion of HSCs in cord blood was higher than that in healthy pregnant women, so as the incidence of neonatal polycythemia in gestational diabetes mellitus (GDM) patients. We aimed to investigate whether the hyperglycemic and/or hyperinsulin environment in GDM patients has effects on the differentiation of HSCs into erythrocytes in offspring cord blood. METHODS In this study, we collected cord blood from 23 GDM patients and 52 healthy pregnant women at delivery. HSCs, CLP, CMP and EPCs in cord blood of the two groups were identified and quantified by flow cytometry. HSCs were sorted out and treated with glucose and insulin, respectively, and then, the changes of HSCs proliferation and differentiation were detected. RESULTS Compared to healthy controls, HSCs, CMP and EPC numbers in cord blood from GDM group were significantly increased, while CLP cell number was decreased. The differentiation of HSCs into EPC was promoted after treatment with glucose or insulin. CONCLUSIONS There were more HSCs in the cord blood of GDM group, and the differentiation of HSCs to EPCs was increased. These findings were probably caused by the high-glucose microenvironment and insulin medication in GDM patients, and the HSCs differentiation changes might be influencing factors of the high incidence of neonatal erythrocytosis in GDM patients.