Supplementary Material for: Neurodevelopmental Changes and Postnatal Growth in the First 3 Years of Extremely Preterm Infants

Introduction
Infants born extremely preterm are at high risk for neurodevelopmental problems. However, their neurodevelopment exhibits a variety of trajectories. This study aimed to investigate the association between changes in neurodevelopmental outcomes and clinical characteristics among extremely preterm infants.
Methods
This is a retrospective study of surviving children born at gestational age 22 to 28 weeks in Kyushu University Hospital between 2010 and 2020. We collected perinatal and post-discharge data, and investigated the association between clinical characteristics and changes in developmental quotient (DQ) scores between 1.5 and 3 years of corrected age.
Results
Out of the 179 eligible extremely preterm infants, 115 (64%) underwent neurological evaluations at 1.5 and 3 years of corrected age. Among them, 33 (29%) showed improvement in their DQ scores (+10 or more), 62 (54%) showed no change (-9 to +9), and 20 (17%) showed a decline (-10 or less). Gestational age, birth weight, and perinatal complications during the NICU stay did not affect individual changes in DQ scores. Multivariable analysis revealed that greater growth in height until age 3 years was a significant predictor of increasing DQ scores, while male sex and having siblings had a negative effect on changes in the DQ scores.

Conclusion
We first demonstrate clinical data conceptualizing that growth in height, sex, and sibling status, rather than perinatal complications, are biologically linked with favorable or unfavorable neurodevelopmental changes of extremely preterm infants during the first 3 years of life.