Supplementary Material for: Outcomes at 18-24 Months of Infants with Birth Weight Under 500 g Born in Korea During 2013–2017: A Nationwide Cohort Study

Introduction: This study aimed to investigate the outcomes of infants at 18-24 months born in the Korean Neonatal Network with a birth weight <500 g. Methods: The anthropometric and neurodevelopmental data of infants with a birth weight <500 g at a gestational age of ≥22 weeks who were registered in the Korean Neonatal Network 2013–2017 and followed up at a corrected age of 18–24 months were reviewed. Neurodevelopmental impairment was defined as the presence of any of the following: (1) cerebral palsy; (2) severe visual impairment; (3) hearing impairment; or (4) cognitive impairment. Cognitive impairment was defined as (1) a Bayley Scales of Infant Development-II Mental Development Index score <70; and (2) Bayley Scales of Infant and Toddler Development-III Cognitive and Language Composite scores <85. Cognitive testing was performed for infants with suspected problems upon clinician’s referral to developmental specialists. Results: At a median corrected age of 20 months, 26/52 (50%) of included infants had neurodevelopmental impairment. Cerebral palsy, severe visual impairment, wearing of glasses, hearing impairment, and cognitive impairment occurred in 22%, 0%, 8%, 5%, and 57% of the included infants, respectively. The proportions of infants with <2 standard deviations of weight, length, and head circumference were 54%, 52%, and 56%, respectively. The majority (70%) of infants were rehospitalized, and the most common cause was respiratory problems. Conclusion: Half of infants with a birth weight <500 g in Korea may exhibit neurodevelopmental impairment and growth retardation at a corrected age of 18–24 months. Multidisciplinary follow-up along with continuous rehabilitation will be needed to improve neurological and physical development in this special population.