MODERATE LOW-BIRTH-WEIGHT AND INFECTIOUS-DISEASE MORTALITY DURING INFANCY AND CHILDHOOD

The purpose of this study was to determine whether moderately low birt h weight, singleton babies without congenital anomalies are at increas ed risk for postperinatal infectious disease mortality. The study coho rt consisted of 54,795 live births assembled at 12 medical school-affi liated hospitals in different regions of the United States between 195 9 and 1966 and followed prospectively. After exclusions of multiple ge station births, very low birth weight (less than 1,500 g) births, birt hs with major congenital anomalies, and first-week deaths, 51,931 chil dren remained for analysis. Postperinatal infectious disease mortality was assessed through age 7 years. Causes of death were classified ind ependently by two pediatricians, blinded to birth weight status, accor ding to an algorithm developed for the study. Moderately low birth wei ght infants and children were at increased risk of infectious disease mortality (relative risk (RR) = 2.49, 95% confidence interval (Cl) 1.7 4-3.55). The risk persisted among those whose deaths met our strictest criteria for infectious etiology and was sustained beyond infancy thr oughout the age interval under analysis. Among those with moderate low birth weight, there was an increased risk among those with preterm bi rth (RR = 2.77, 95% CI 1.19-6.46) but not among those who were born sm all-for-gestational age (RR = 1.19, 95% CI 0.37-3.83). The data sugges t that moderate low birth weight renders individuals vulnerable to inf ectious disease mortality during both infancy and childhood. Among mod erately low birth weight infants and children, this vulnerability appe ared to be attributable primarily to preterm birth rather than to intr auterine growth retardation.