223 - Evaluating Corrected Versus Uncorrected Bayley-IV Scoring at 24 Months in Preterm Infants: Implications for Developmental Testing

Publication Number: 4220.223

Dina Yacoub, Brigham and Women's Hospital, Boston, MA, United States; Melina M. Hammoud, Brigham and Women's Hospital, Boston, MA, United States; Emma Adkins, Brigham and Women's Hospital, Brookline, MA, United States; Melissa A. Woythaler, Brigham and Women's Hospital, Boston, MA, United States

Background: Preterm infants are at increased risk for developmental delays across cognitive, language, and motor domains. The Bayley Scales of Infant and Toddler Development, Fourth Edition (Bayley-IV), are commonly used at 24 months to assess developmental outcomes. Although the Bayley-IV manual recommends discontinuing age correction at 24 months, many preterm infants continue to show developmental differences proportional to their degree of prematurity. The decision to correct or not correct for prematurity at this age influences score interpretation and service eligibility.

Objective: To compare corrected and uncorrected Bayley-IV scores in preterm infants at 24 months with full-term norms and evaluate whether gestational age (GA) affects the magnitude of score deviation.

Design/Methods: This retrospective cohort included infants born July 2019-August 2024 and evaluated at 24 months corrected age (22m0d-25m30d) at a developmental follow-up clinic. Of 927 infants, 219 met criteria (GA 24-34 weeks with complete visit data). Standard scores for cognitive (COG), receptive communication (RC), expressive communication (EC), fine motor (FM), and gross motor (GM) domains were analyzed using corrected and uncorrected age scoring. One-sample z-tests compared mean scores by GA to standardized full-term norms (COG mean 100±15; RC/EC/FM/GM mean 10±3; p< 0.05).

Results: As shown in Table One, mean COG corrected scores were lower than norms only at GA 24 weeks, while uncorrected scores were lower across GA < 34 weeks (Figure One). RC corrected scores were lower at GA 24, 25, and 31 weeks; uncorrected scores were lower at GA 24-25 and 27-32 weeks. EC corrected scores were lower at GA 24, 25, 29, 31, and 33 weeks; uncorrected scores were lower across GA < 34 weeks. FM corrected scores were lower only at GA 24 weeks; uncorrected scores were lower across GA < 32 weeks. GM scores were lower across GA < 34 weeks for both scoring methods (Figure Two). Overall, uncorrected scoring consistently identified a greater proportion of infants as delayed across all developmental domains.

Conclusion(s): Corrected scoring primarily identified developmental differences in extremely preterm infants, whereas uncorrected scoring detected delays across a broader GA range. Findings support continued use of corrected age at 24 months to more accurately reflect developmental progress and minimize misclassification of delays. Maintaining age correction at this time point may improve the validity of developmental assessment and ensure appropriate access to early intervention for preterm populations.

Table One: Comparison of Corrected vs. Uncorrected Bayley-IV Scores by Gestational Age
Mean standardized Bayley-IV scores are presented by gestational age (24-34 weeks) for cognitive (COG), receptive communication (RC), expressive communication (EC), fine motor (FM), and gross motor (GM) domains. Corrected and uncorrected scores were compared to full-term normative means (COG: 100 ± 15; RC/EC/FM/GM: 10 ± 3). Asterisks indicate scores significantly lower than Bayley-IV norms (p < 0.05).

Figure One: Mean Corrected vs. Uncorrected Bayley-IV Cognitive Scores by Gestational Age
Mean corrected vs. uncorrected Bayley-IV cognitive scores by gestational age. Corrected scores are consistently higher than uncorrected scores across all gestational ages, with both measures approaching the normative mean (100) as gestational age increased.

Figure Two: Mean Corrected vs. Uncorrected Bayley-IV Gross Motor Scores by Gestational Age
Mean corrected and uncorrected Bayley-IV Gross Motor scores by gestational age. Corrected scores are consistently higher than uncorrected scores across gestational ages, with both remaining below the Bayley-IV normative mean of 10.