Updated Swiss Growth References 2025: No Height Differences, but BMI Variations Associated with Migration

Background/Objectives: The 2019 Swiss growth references for height, weight, and BMI were based on a large dataset from the German-speaking part of Switzerland (Cohort 2019). The current study aimed to ensure national representativeness by proportionate amounts of additional data from the French-speaking (Suisse Romande) and Italian-speaking (Ticino) regions to validate the 2019 growth curves and to update the national growth references. It also investigated the influence of parental migration background on child growth. Methods: Anthropometric data from 43,290 children and adolescents—including 11,816 new cases—were analyzed (Cohort 2019 + 2025). Percentile curves were modeled using the Generalized Additive Models for Location, Scale, and Shape (GAMLSS) framework. Results: The extended dataset largely confirms the 2019 growth references. Variations in height percentiles were small and clinically negligible. Clinically relevant differences in BMI percentiles were observed in girls, with the most pronounced deviations—up to 0.8 kg/m²—at the 97th percentile. Analyses by parental migration background revealed relevant differences in BMI. Conclusions: The extended Swiss Growth References (Cohort 2019 + 2025) are robust and provide valid reference data for all Swiss children and adolescents, offering contemporary tools for decision-making in clinical practice. To maintain their validity over time, targeted updates are required, with special attention to demographic changes resulting from migration.