When surgery is performed on pregnant women forthe sake of the fetus (MFS or maternal fetalsurgery), it is often discussed in terms of thefetus alone. This usage exemplifies whatphilosophers call the fallacy of abstraction: considering a concept as if it were separablefrom another concept whose meaning isessentially related to it. In light of theirpotential separability, research on pregnantwomen raises the possibility of conflictsbetween the interests of the woman and those ofthe fetus. Such research should meet therequirement of equipoise, i.e., a (...) state ofgenuine uncertainty about the risks andbenefits of alternative interventions ornoninterventions. While illustrating thefallacy of abstraction in discussions of MFS,we review the rationale for explicitacknowledgment of the essential tie betweenfetus and pregnant woman. Next we examinewhether it is possible to meet the requirementof equipoise in research on MFS, focusing on afetal condition called myelomeningocele. Weshow how issues related to equipoise innonpregnant populations appear also in debatesregarding MFS. We also examine evidence insupport of claims that the requirement ofequipoise has been satisfied with respect to``the fetal patient'' while considering risks andbenefits to gestating women only marginally ornot at all. After delineating challenges andpossibilities for equipoise in MFS research, weconclude with a suggestion for avoiding thefallacy of abstraction and achieving equipoiseso that research on MFS may be ethicallyconducted. (shrink)