One investigated the social and biological determinants of infant mortality of a population cohort of 2,331 live births in the period February 2003 to January 2004, in the city of Passo Fundo, Rio Grande do Sul State, including 56 infant deaths. The databank of deaths had been increased to the databank of the birth cohort, which contained the social and biological variables obtained from live birth certificates and with home interviews. The coefficient of infant mortality of this cohort was 22.8%. Multivariate analyses with logistic regression and hierarchic model had shown that the following aspects were significantly associated with infant death: maternal educational level lower than eight years (RR= 5.7; IC 95%: 1.92- 16.75), antecedent of dead children (RR= 3.7 (IC 95%: 1.07-12.10); low birth weight, with RR= 6.7 (IC 95%: 2.07-21.65) to 79.7 (IC 95%:14.36-441.92) for infants of low birth weight and weighing less than 1500g, respectively; Apgar scores < 7 (RR=8.7; IC 95%: 2.85-26.32) and absence of breastfeeding (RR=15.75; IC 95%: 6.7663.68). As infant mortality in Passo Fundo is socially determined by the low maternal educational level and biologically determined by birth conditions, low birth weight and interruption of breastfeeding, one recommend the inclusion of these factors in the classification of risk for follow up of infant mortality in Passo Fundo.
Cohort studies; Epidemiologic factors; Infant mortality