Sex-Specific Developmental Scales for Surveillance

Developmental surveillance, conducted routinely worldwide, is fundamental for early detection of children at risk for developmental delay. We aimed to explore sex-related difference in attainment rates of developmental milestones and to evaluate the clinical need for separate sex-specific scales.

This is a cross-sectional, natiowide retrospective study, utilizing data from a national child surveillance program of ∼1000 maternal child health clinics. The main cohort, used for constructing sex-specific developmental scales, included all children born between January 2014 to September 2020, who visited maternal child health clinics from birth to 6 years of age (n = 839 574). Children with abnormal developmental potential were excluded (n = 195 616). A validation cohort included all visits between 2020 and 2021 (n = 309 181). The sex-differences in normative attainment age of 59 developmental milestones from 4 domains were evaluated. The milestones with a significant gap between males and females were identified, and the projected error rates when conducting unified versus sex-specific surveillance were calculated.

A new sex-specific developmental scale was constructed. In total, females preceded males in most milestones of all developmental domains, mainly at older ages. Conducting routine developmental surveillance using a unified scale, compared with sex-specific scales, resulted in potential missing of females at risk for developmental delay (19.3% of failed assessments) and over-diagnosis of males not requiring further evaluation (5.9% of failed assessments).

There are sex-related differences in the normative attainment rates of developmental milestones, indicating possible distortion of the currently used unified scales. These findings suggest that using sex-specific scales may improve the accuracy of early childhood developmental surveillance.