Currently, treatment for many childhood blood-related illnesses is complicated by the therapies necessary to ensure transplanted cells persist, are effective, and do not result in further complications that compromise health. These studies focus on ways to provide treatments before birth in a safe and efficient manner, and to address bottlenecks such as the expansion of cells prior to transplantation that would be needed to be curative, and methods to safely monitor the cells post-transplant in young individuals. Cells of interest include umbilical cord blood cells and more primitive hematopoietic precursors obtained from human embryonic stem cells. Our studies have shown effective methods for expanding these cell populations, collecting them in a clinically acceptable manner, and assessing their use for transplantation. Studies continue to explore the safety and efficiency of these novel therapies for fetuses diagnosed in utero with inherited blood cell disorders, and the use of in vivo imaging to monitor the cells safely post-transplantation.