The rapidly evolving ability to detect the presence of major anomalies in the developing fetus and the emerging prospect of intrauterine treatment of some of these disorders are coupled to create an exciting new frontier in care of the high-risk pregnancy. Preliminary reports suggest that in some highly selected instances perinatal death and morbidity may be prevented by intrauterine surgical procedures. The technical ability to treat the disorder as described is at hand and is unlikely to be the limiting factor in the advance of this area of fetal treatment. However, the very fact that treatment is possible cannot be considered as proof of efficacy. The physician faced with the knowledge that a potentially treatable condition is present in a given fetus may feel the necessity of instituting treatment, but the validity of such an approach is far from established. It is our opinion that efforts should be made to set at the earliest point proper controlled scientific studies from which the benefit, if any, of this surgical approach to fetal disease may be established. Such clinical studies should be conducted in concert with studies in appropriate animal models. It should be noted that fetal surgical treatment is not without potentially lethal fetal and maternal complications. Before such risks, however small, are taken, it seems reasonable to determine the long-term benefits of the surgical procedure. To this end, participation in the International Fetal Surgery Registry is encouraged.