Low weight/length ratio at birth is associated with hospitalizations during the first year of life: a cohort study.

The aim is to study the association of a low birth weight/length ratio (W/L) with the risk of hospitalizations during the first year of life (YOL). Cohort study of live births from Ribeirão Preto, Brazil in 2010 and 2011. Low W/L was defined as below the 3rd percentile for gestational age (GA) and sex according to the Intergrowth 21st. Single and multiple Cox proportional hazards models were modelled. 4,087 children were included, of which 741 (18.1%) had been hospitalized at least once during the first YOL. In the univariate analysis, the factors associated with increased risk of the outcome were: low W/L, inadequate prenatal care, maternal hypertension, black skin color, and using the public health system. In the multivariate analysis, a low birth W/L was associated with greater risk of all hospitalizations [adjusted hazard ratio (aHR) 2.67, 95% confidence interval [95%CI] 1.98, 3.60], but this association disappeared when we excluded neonatal hospitalizations (aHR 1.58, 95%CI 0.98, 2.54). A low birth W/L for GA and sex was not associated with an increased risk of hospitalizations during the first YOL beyond the neonatal period in a Brazilian cohort of live births.