It is anticipated that in utero stem cell transplantation and in utero gene therapy will hold great promise in the treatment of a wide range of genetic disorders that may be discovered before birth. Before in utero stem cell transplantation and in utero gene therapy can be used in the clinic, it is necessary to properly investigate the ethical and safety problems involved. Future animal studies, as well as human studies, will be required to determine the likelihood and consequences of maternal exposure to medicine.