Non-supine infant sleep position is an important modifiable risk factor for sudden unexpected death in infancy. The aim of this study was to assess the prevalence of supine sleep position and associated factors among 3-month-old infants from a birth cohort in the city of Pelotas, southern Brazil. | Prevalence and associated factors of supine sleep position in 3-month-old infants: Findings from the 2015 Pelotas (Brazil) Birth Cohort