This thesis is about infancy, independence, and how medicalisation shapes mothers' perceptions of their infants. It draws on ethnographic research in Cardiff, undertaken during a period of heightened concern about the Sudden Infant Death Syndrome (SIDS), and funded by the Foundation for the Study of Infant Deaths. Three "cultural constructions" of infancy are juxtaposed: the vulnerable and constantly accompanied Bangladeshi infant, the Welsh or English infant encouraged towards independence, and the autonomous infant of epidemiological analysis. The thesis shows how the processes of medicalisation brought contrasting perceptions of infancy to light, suggesting that Bangladeshi women taking part in an "English for Pregnancy" project were not only learning language, but also learning about medicalised infant care. It argues too that health professionals shape the way in which mothers perceive their infants through the introduction of the language of "risk factors". The infant body itself emerged at the boundary of powerful systems of meaning. If the boundaries of the Bangladeshi infant body were blurred through constant contact, those of the Welsh or English infant were marked intermittently through alternating periods of solitude with "attention". Some Welsh and English mothers spoke of infants and their care in terms of the care of domestic animals, and the mothers' own ambivalence about their own animality, while some Bangladeshi mothers spoke of the spiritual power and vulnerability of infants, and in doing so articulated their links with Bangladesh. For health professionals the infant body was a site for demonstrating expertise through both research (which constructed ethnic minorities as 'natural') and recommendations for action. The thesis discusses the location of contemporary anthropology at cultural boundaries. Juxtaposing contrasting beliefs about infancy revealed very different perceptions of independence, marked in particular by contrasting perceptions of time, space, and the infant body itself.