Nucleated red blood cells (nRBCs) are immature red blood cells, which are rarely in circulating blood in elder children, but often present in neonatal blood. The clinical significance in neonates is unclear. Numerous studies have shown that many kinds of acute and chronic stimuli can lead to an increase in the number of nRBCs in circulating blood. This article reviews various pathological processes related to the production and release of nRBCs, and emphasizes the effects of acute and chronic hypoxia and immune regulation on it.