OBJECTIVES: To determine neurodevelopmental outcomes at 3 years of age in children born with a birth weight (BW) of ≤500 g. METHODS: Infants who were born with a BW of ≤500 g from 2003 to 2012 in the Neonatal Research Network of Japan and survived to discharge from the NICU were eligible in this study. The study population consisted of 460 children (56.7% of 811 surviving infants) who were evaluated at 36 to 42 months of age. Neurodevelopmental impairment (NDI) was defined as having cerebral palsy, visual impairment, hearing impairment, or a developmental quotient score of <70. RESULTS: The overall proportion of NDI was 59.1% (95% confidence interval [CI]: 54.6%-63.5%). The trend revealed no significant change during the study period. In a multivariate modified Poisson regression analysis, NDI was associated with severe intraventricular hemorrhage (adjusted risk ratio [RR]: 1.42; 95% CI: 1.19-1.68; P <.01), cystic periventricular leukomalacia (adjusted RR: 1.40; 95% CI: 1.13-1.73; P <.01), severe necrotizing enterocolitis (adjusted RR: 1.31; 95% CI: 1.07-1.60; P <.01), surgical ligation for patent ductus arteriosus (adjusted RR: 1.29; 95% CI: 1.09-1.54; P <.01), and male sex (adjusted RR: 1.19; 95% CI: 1.01-2.40; P =.04). CONCLUSIONS: This cohort showed that neurodevelopmental outcomes of infants with a BW of ≤500 g have not improved from 2003 to 2012. Multivariate analysis revealed that severe intracranial hemorrhage and cystic periventricular leukomalacia were the strongest risk factors for NDIs. Our data suggested that measures aimed at reducing neurologic morbidities will be important for improving outcomes of infants with a BW of ≤500 g.
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