Factors associated with infant and adolescent mortality.

Few studies have described factors associated with infant and adolescent mortality since birth. We report here mortality during a 20-year period in a birth cohort from Ribeirão Preto in order to identify birth variables that influenced mortality among infants and children between 10 and 19 years of age, the main causes of death, and the influence of social inequality at birth on death. Mothers were interviewed shortly after delivery. Social, biological and demographic information was collected, and mortality up to 19 years of age was investigated in registry systems. Of the 6748 liveborn singletons born in the municipality from 1978 to 1979, 343 died before or when 19 years of age were completed. Most of the cohort mortality (74.9%) occurred during the first year of life and 19.6% occurred from 10 to 19 years. Mortality was higher among boys. Preterm birth (hazard ratio, HR = 7.94) and low birth weight (HR = 10.15) were strongly associated with infant mortality. Other risk factors for infant mortality were: maternal age (3)35 years (HR = 1.74), unskilled manual occupation of family head (HR = 2.47), and for adolescent mortality: unskilled manual occupation of family head (HR = 9.98) and male sex (HR = 6.58). "Perinatal conditions" were the main causes of deaths among infants and "external causes" among adolescents, especially boys. Socioeconomic factors at birth, represented by occupation, influenced adolescent mortality due to external causes, which was higher among boys (7:1). The influence of social inequality at birth on death, measured by occupation, was greater in adolescence than in infancy.