Current management of isoimmunization in pregnancy is predicted on the assumption that all sensitized women carry antigen-positive fetuses. In addition, management is based on indirect predictors of the magnitude of the fetal hemolytic disease. We present a preliminary report using a new approach of direct fetal blood sampling for the diagnosis and treatment of these patients. This form of evaluation provides specific information about fetal red blood cell antigen status and the degree of fetal anemia at an earlier gestational age than that validated by the Liley curves and eliminates empiricism from both the diagnosis and treatment of the isoimmunized pregnancy. The use of such a management protocol reduces the need for multiple invasive procedures in fetuses at little risk for disease and provides specific information about the status of those fetuses truly at risk.