Gestational age-specific sex difference in neurological outcomes of very low birth weight preterm infants—a nationwide study

This is a population-based study from the Korean Neonatal Network (KNN) for very low birth weight infants (VLBWIs) born at 23⁺⁰ and 31⁺⁶ weeks of gestation between 2013 and 2019. This study aims to evaluate the effect of sex on neurological outcomes at 18–24 months corrected age, stratified with gestational age (GA) in VLBWIs. A total of 1,829 infants (15.7%) who completed Bayley Scales of Infant and Toddler Development, third edition (BSID-III) assessments at 18–24 months corrected age were included and were further stratified into three GA groups: 23⁺⁰ to 25⁺⁶ weeks, 26⁺⁰ to 28⁺⁶ weeks, and 29⁺⁰ to 31⁺⁶ weeks. The primary outcomes were the BSID-III composite scores and neurodevelopmental delay defined as BSID-III composite scores lower than 80. Male sex was an independent risk factor for neurodevelopmental delay, particularly in infants born over 26 weeks of gestation. Among VLBW preterm infants born over 26 weeks of gestation, male infants of the younger GA group were associated with a higher risk of cognitive and motor delay, whereas those of the older GA group had a higher risk of language delay. The extremely low GA group (below 25 weeks of gestation) did not exhibit sex differences in neurodevelopmental outcomes.