Neonatal expertise and technologies have been perfected over the last decades, improving preterm infants' survival rates and allowing a gradual reduction in the gestational age limits of fetal viability. Using the concept of viability as a starting point, we analyze decision-making processes regarding extremely preterm newborns at the limits of viability. Drawing on extensive ethnographic fieldwork in a public hospital in Barcelona between March and November 2023, we examine the knowledge forms, rationalities and values that healthcare workers employ when guiding families in decisions about infants' viability. In this respect, we thoroughly analyze the actors involved and the extent of their agency. The findings point out that although neonatal decisions in Spain are embedded in an ethos of "individual responsible choice," they are in practice collectively produced and shaped by two main (sometimes conflicting) drivers: the perceived means of families to face the challenges posed by infants with high chances of severe sequelae (the 'viability of families'), and the preterm patients' perceived "will to live" ('fetal viability'). The study highlights how viability in this context needs to be understood within the structural socioeconomic constraints and struggles to make and raise families in Spain.