In utero stem cell transplantation for the treatment of genetic diseases.

In utero haematopoietic cell transplantation is currently in its embryonic stage of development, but holds considerable developmental promise as a therapeutic approach for the treatment of a large number of congenital haematological diseases. Despite, until recently, limited evidence of clinical efficacy, interest in the field has been gaining momentum, and clinical application is likely to increase. Parallel advances in prenatal diagnosis, fetal intervention, and haematopoietic stem cell technology have removed many of the practical, technical, and ethical obstacles to clinical application. With this progress, there has been a significant increase in the number of centers around the world with both the stated interest and perceived expertise to develop clinical programs. At this point in the evolution of in utero haematopoietic stem cell transplantation there are more questions than answers. Widespread clinical applications are premature based on the extremely limited clinical success, which has been achieved. The biology of each disease is unique and expectations of success or failure can only be based upon sound clinical investigation guided by an understanding of the relevant issues and careful selection and evaluation of patients. Clinical centers should be associated with an active research effort to solve the remaining problems with this potentially valuable therapeutic approach. In the near future, advances in our understanding of stem cell biology, developmental ontogeny, and gene therapy may allow prenatal stem cell and gene therapy to achieve their full potential.