Currently, the treatment for many childhood illnesses are complicated by the therapies necessary to ensure transplanted cells persist, are effective, and do not result in health complications. These studies focus on ways to provide treatments prenatally before birth safely and efficiently, and to address bottlenecks such as the expansion of cells that would be useful for transplantation. These include umbilical cord blood cells and more primitive precursors obtained from human embryonic stem cells. Our studies have shown effective methods for expanding these cell populations, and assessing their use for transplantation. Studies continue to explore the safety and efficiency of these novel therapies for fetuses diagnosed in utero with an inherited blood cell disorder.