Neurodevelopment at Age 9 Years Among Children Born at 32 to 36 Weeks' Gestation.

Importance: Although children born moderate to late preterm (MLP; 32-36 weeks' gestation) have more neurodevelopmental problems compared with children born early term or later (≥37 weeks' gestation), detailed understanding of affected domains at school age is lacking. Little is known of risk factors for poorer development. Objective: To examine whether being born MLP compared with being born early term or later is associated with neurodevelopmental outcomes at age 9 years and to describe factors associated with poorer neurodevelopment in children born MLP. Design, Setting, and Participants: This prospective, longitudinal cohort study recruited children born MLP and children born early term or later with healthy birth weight (≥2500 g) at a single tertiary hospital in Melbourne, Victoria, Australia, between December 7, 2009, and March 26, 2014. Nine-year follow-up occurred between June 20, 2019, and February 27, 2024. Exposure: Moderate to late preterm birth. Main Outcomes and Measures: Cognitive ability, academic performance, motor function, behavior, and social communication skills, assessed at 9-year follow-up. Group differences were estimated using linear, logistic, or quantile regression adjusted for multiple birth and socioeconomic risk. Multiple imputation was used to account for missing data. Associations of antenatal and neonatal factors and developmental delay at 2 years with poorer 9-year neurodevelopment were explored using univariable regression. Results: Of 201 recruited children born MLP and 201 born early term or later, 159 born MLP (79.1%; 72 [45.3%] male) and 137 born early term or later (68.2%; 75 [54.7%] male) were assessed. Compared with children born early term or later, children born MLP had lower mean (SD) full-scale IQ scores (105.2 [13.6] vs 110.1 [13.0]; adjusted mean difference, -4.4 [95% CI, -7.7 to -1.0]) and poorer performance for cognitive domains, including verbal comprehension, visuospatial, and working memory. They also had poorer academic performance: pseudoword decoding (mean [SD] score, 103.0 [11.3] vs 107.3 [10.5]; adjusted mean difference, -4.0 [95% CI, -7.0 to -1.1]) and mathematics (mean [SD] score, 96.6 [14.7] vs 101.5 [14.5]; adjusted mean difference, -5.0 [95% CI, -8.8 to -1.2]). Children born MLP had similar manual dexterity to those born early term or later (mean [SD] score, 8.4 [3.5] vs 9.1 [3.4]; adjusted mean difference, -0.9 [95% CI, -1.8 to 0.04]) but more behavioral difficulties (50 of 158 [31.7%] vs 29 of 135 [21.5%]; adjusted risk ratio, 1.57 [95% CI, 1.06-2.33]). Developmental delay at 2 years was associated with poorer 9-year neurodevelopment across multiple domains. Conclusions and Relevance: In this longitudinal cohort study of children born MLP, neurodevelopmental challenges persisted into school age. An assessment at age 2 years may assist in identifying children born MLP who are at risk of school-age impairments.