Fig. 1

Flow Chart of Selection of Study and Comparison Subjects from Patients registered in Taiwan’s Longitudinal Health Insurance Research Database (LHID), a subset of the Taiwan’s National Health Insurance Research Database. Propensity score matching by: the family’s levels of income and neonatal data (including sex, birth weight, blindness and low vision, infections specified to the perinatal period, necrotizing enterocolitis in fetus or newborn, epilepsy, fetal and neonatal hemorrhage, communicating hydrocephalus, intrauterine hypoxia and birth asphyxia, other perinatal jaundice, microcephalus, patent ductus arteriosus, pneumonia, pneumothorax, respiratory distress syndrome, other respiratory conditions of fetus and newborn). MLBW marginally low birth weight, defined as birth weight between 2000 and 2499 g