Weighted and unweighted comorbidity burden for predicting three-year neurodevelopment in extremely preterm infants: A nationwide cohort study.

OBJECTIVE: To compare the prognostic utility of unweighted morbidity counts and weighted morbidity scores for predicting neurodevelopmental outcomes at 3 years in extremely preterm infants. STUDY DESIGN: This retrospective cohort study used data from the Neonatal Research Network of Japan and included infants born at <28 weeks' gestation. Neurodevelopment at 3 years was assessed using developmental quotient and cerebral palsy. Cumulative morbidity burden was quantified using unweighted morbidity counts and weighted morbidity scores derived from log-odds ratios for severe impairment. Inverse probability weighting addressed incomplete follow-up. RESULTS: Both unweighted morbidity counts and weighted morbidity scores were significantly associated with adverse neurodevelopmental outcomes. Unweighted morbidity counts demonstrated higher sensitivity for identifying any adverse outcome, whereas weighted morbidity scores showed high specificity (0.94) for severe impairment. CONCLUSION: Unweighted morbidity counts and weighted morbidity scores provide complementary prognostic information and may improve risk stratification, follow-up prioritization, and family counseling for extremely preterm infants.