The impact of birth weight on infectious disease hospitalization in childhood.

Low birth weight, a result of preterm birth or intrauterine growth restriction, is a well-established indicator of survival in childhood. However, corresponding epidemiologic studies of the association between low birth weight and morbidity from infections throughout childhood are sparse. The authors evaluated the relation between birth weight and infectious diseases throughout childhood in a population-based cohort study comprising all children born in Denmark from 1977 through 2004 (n = 1.7 million). Information on birth weight, gestational age, and potential confounding variables was linked to the children in the cohort, together with information on hospitalization with infectious disease. Poisson regression yielded rate ratios of hospitalization according to birth weight. The authors found that birth weight was inversely associated with risk of infectious disease hospitalization; among children aged 0-14 years, the risk of hospitalization increased 9% for each 500-g reduction in birth weight (increase in rate ratio = 1.09, 95% confidence interval: 1.09, 1.11). The effect was found to peak in infancy and to persist until 10 years of age. It was present also in children born at term (37-41 weeks of gestation). The present study is the first to demonstrate the measurable impact of birth weight on infectious diseases throughout childhood.