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Comparison of the 2025 Third-Generation and 2013 Fenton Growth Charts in Preterm Infants Born before 35 Weeks: A
Dumisani Kamwana1, Venkateshwarlu Vardhelli1, Nicholas Hoque1,2
1Kanad Hospital, Department of Neonatology, Abu Dhabi, United Arab Emirates, Al Ain.
Objective:
This study aimed to compare the classification of birth size using the Fenton 2025 third-generation growth charts versus the widely used Fenton 2013 charts in preterm infants born before 35 weeks' gestation.
Study Design:
This retrospective, observational cohort study included preterm infants born at <35 weeks' gestation and admitted to a tertiary-level neonatal intensive care unit (NICU) between January 2019 and August 2025. Birth weight, head circumference (HC), and length were classified using sex-specific Fenton 2013 and Fenton 2025 growth chart calculators. Infants were categorized as small for gestational age (SGA, <10th percentile), appropriate for gestational age (AGA, 10th-90th percentile), or large for gestational age (LGA, >90th percentile). Agreement between chart versions was assessed using weighted Cohen's kappa, and marginal distributions were compared using the Stuart-Maxwell test.
Results:
A total of 1,121 infants (56.9% male) were included, with a mean (standard deviation) gestational age of 31.6 (3.2) weeks and birth weight of 1,648 (595) g. Overall agreement between the two chart versions was high for all anthropometric measures. For birth weight, overall concordance was 87.2%, with moderate agreement (κ = 0.64). The proportion classified as SGA increased from 12.0% using Fenton 2013 to 23.0% using Fenton 2025 (p = 0.001), reflecting a downward shift in birth weight z-scores and reclassification of 13.2% of infants from AGA to SGA. Agreement was stronger for HC (93.5%, κ = 0.80) and length (96.3%, κ = 0.90), with minimal reclassification. Classification differences varied by gestational age, with greater shifts observed at later preterm gestations.
Conclusion:
In preterm infants born before 35 weeks' gestation, the Fenton 2025 growth charts demonstrate high overall agreement with the Fenton 2013 charts but identify a substantially higher proportion of infants as SGA based on birth weight. These differences may have important clinical and research implications and warrant careful consideration.
Key Points:
· Fenton 2025 identifies more SGA preterm infants.. · Birth weight shows the greatest classification change.. · Reclassification of birth weight predominates around the 10th percentile..
