Winner of the Polgar Prize for Best Article, Society of Medical Anthropology ~ Even in a country with super-low fertility rates, at least one-quarter of all babies are unplanned. The finding puzzles policymakers. This article uses Italy’s “curious case” as a jumping-off point to expose assumptions about rationality. It offers a model to dismantle the “conceit” of rationality, drawing on Max Weber’s classic critique and Emily Martin’s contemporary appraisal. It asks: (1) How do assumptions about rationality related to sexuality and reproduction manifest? (2) How do qualitative data challenge rationalist assumptions? and (3) How are cultural logics expressed and what do they reveal about the “problem” of low fertility? Methodologically, the article offers an innovative approach, juxtaposing ethnographic data derived from the author’s fieldwork with startling findings from Italian researchers’ multicity project. The analysis exposes the rationality trope as a technique of governance in a context in which policymakers yearn for social cohesion and population politics intensify around birthing, immigration, and aging. [rationality, fertility, politics of reproduction, Italy, Europe]