When surgery is performed on pregnant women for the sake of the fetus (MFS or maternal fetal surgery). it is often discussed in terms of the fetus alone. This usage exemplifies what philosophers call the fallacy of abstraction: considering a concept as if it were separable from another concept whose meaning is essentially related to it. In light of their potential separability, research on pregnant women raises the possibility of conflicts between the interests of the woman and those of the fetus. Such research should meet the requirement of equipoise. i.e., a state of genuine uncertainty about the risks and benefits of alternative interventions or noninterventions. While illustrating the fallacy of abstraction in discussions of MFS, we review the rationale for explicit acknowledgment of the essential tie between fetus and pregnant woman. Next we examine whether it is possible to meet the requirement of equipoise in research on MFS, focusing on a fetal condition called myelomeningocele. We show how issues related to equipoise in nonpregnant populations appear also in debates regarding MFS. We also examine evidence in support of claims that the requirement of equipoise has been satisfied with respect to “the fetal patient” while considering risks and benefits to gestating women only marginally or not at all. After delineating challenges and possibilities for equipoise in MFS research, we conclude with a suggestion for avoiding the fallacy of abstraction and achieving equipoise so that research on MFS may be ethically conducted.