Although recent advances have helped identify cases where foetal cardiac surgery might reverse the development of certain lesions, the indications and measurement of success in these procedures have yet to be established. Thus, both patients and physicians have a “burden of knowledge”, whereby a diagnosis is made without a clear course of action. The profound issues raised by foetal intervention, specifically the question of how concepts such as “patient” and “success” can be used, complicate this burden further and test the limits of language and logic. Similar issues raised in postmodern philosophy are discussed and can be incorporated into foetal cardiac surgery dialogues to produce a multi-disciplinary approach that will elucidate, not obfuscate, these issues in the future.