Influence of birth weight on mortality from infectious diseases: a case-control study.

The association between birth weight and infant mortality from infectious diseases was investigated in a population-based case-control study in two urban areas in southern Brazil. All deaths of children, seven to 364 days of age, occurring in a year were studied and the parents of the 357 infants dying of an infectious cause were interviewed, as were the parents of two neighborhood control infants for each case. Low birth weight infants (less than 2,500 g) were found, after allowing for confounding factors, to be 2.3 (90% confidence interval = 1.6 to 3.4) times more likely to die of an infection than those of higher birth weight. The odds ratios were 2.0 (1.1 to 3.6) for deaths due to diarrhea, 1.9 (1.0 to 3.6) for respiratory infections, and 5.0 (1.3 to 18.6) for other infections. These estimates of the risks associated with low birth weight are considerably lower than those from studies in developed countries.