Age-corrected development of preterm children: a population-based study

Background: The standard practice to account for expected developmental lags in preterm children is calculating their age as if born on their expected delivery date. We aimed to assess the accuracy of standard age correction in a large and diverse population. Methods: Routine surveillance data was extracted from a national network of mother-child clinics covering over 70% of the Israeli population. We included children with no developmental delay at age 2 years old, to exclude chronic dysfunctions. For each milestone assessed before age 2 years old we calculated the age of 90% and 95% population-milestone attainment, and compared attainment age between term and preterm children, before and after age correction. Results: The study consisted of n = 656,986 and n = 52,662 term and preterm children respectively. Without age correction extensive gaps were observed in all domains, all degrees of prematurity and persisted throughout the first 2 years of life. With age correction most gaps were resolved among moderate/late preterm children, but not among extreme and very preterm, with residual gaps of at least 2 months for motor and 1 month for language-social development. Conclusion: While standard age correction accounts for maturational delay in late/moderate preterm children, it may underestimate the maturational delay among very/ extremely preterm children. Impact: Standard age correction is sufficient for late/moderate preterm children, and underestimates the maturational delay of extreme and very preterm children. Prior evidence on the accuracy of standard age correction across developmental domains and degrees of prematurity was limited to dated, small-scale data. Maturational delays persist throughout the first 2 years of life across all developmental domains and in all levels of prematurity. Developmental assessments without age correction may lead to unnecessary parental anxiety.