Stability of developmental milestones: Insights from a 44-year analysis.

Using standardized test procedures is a reliable way of assessing early childhood development in the pediatric setting. However, normal population's developmental parameters may change over time. The aim of this study was to determine whether a change of developmental percentiles is present in infants in Germany during recent decades. Measured by an established German diagnostic instrument (Münchener Funktionelle Entwicklungsdiagnostik) we cross-sectionally compared developmental data (cognition, expressive language, language comprehension, fine and gross motor skills, social development, daily-living skills) of children aged 0-36 months collected in the 1970s and in 2018. N = 2065 children and their parents were included (1970s sample: N = 1660 and 2018 sample: N = 405). The T-Test of dependent variables showed nonsignificant differences in the developmental scales. We hypothesized an infant Flynn effect, but the results of this study suggest that there are no developmental changes associated with the 50th percentile. Nevertheless, it is critical to emphasize the need for periodic revision and re-norming of developmental test procedures, even in the absence of significant changes in individual items.