Low birthweight as a determinant of infectious disease mortality: a methodological evaluation

Abstract

Low birthweight (LBW) is cited as an important determinant of infectious disease mortality during infancy, both in developed and developing countries. We applied methodological standards to evaluate the scientific validity and clinical applicability of epidemiological studies of this relationship. Three published studies, all reporting an elevation of the risk of infectious disease mortality in infants born with LBW, were identified. Noteworthy methodological deficiencies found in one or more studies included failure to obtain objective data about birthweight and gestational age for a high proportion of study subjects, lack of explicit criteria for assigning causes of death, failure to safeguard against biases in assessment of cause of death and inadequate control for potential confounding variables. In addition, clinical application of the results of these studies was limited by lack of exploration of the roles of preterm birth vs. small-for-gestational-age (SGA) birth, as well as by inattention to the role of congenital anomalies, in explaining the elevated risk. Although our evaluation does not necessarily negate the results of these studies, the failure of any of the studies to comply with all of the standards highlights the need for further research to provide credible evidence regarding the presence and strength of a relationship between LBW and infectious disease mortality in both developed and developing countries.