Family structure and birth order in relation to preschoolers' social, emotional, and behavioral outcomes: a cross-sectional analysis of 19,987 children in western China.

Introduction: Family structure and birth order are cross-sectionally associated with preschoolers' social, emotional, and behavioral outcomes, yet their specific implications in diverse family contexts require further exploration. Methods: This cross-sectional study assessed social, emotional, and behavioral outcomes in 19,987 preschoolers (ages 3-6) across 189 kindergartens in western China using the Strengths and Difficulties Questionnaire (SDQ). Multivariate logistic and linear regression models were employed to evaluate associations, adjusting for demographic, socioeconomic, and behavioral covariates, with additional stratified and sensitivity analyses to test robustness. Results: A total of 19,987 preschoolers (51.6% boys) were included. Compared with only children, multi-child family status was associated with lower odds of prosocial behavior (OR = 0.90, 95% CI: 0.83-0.98, Conclusion: This cross-sectional study of 19,987 preschoolers found that multi-child families had lower prosocial behavior and higher externalizing risk than only children. First-born children showed higher externalizing risks and lower prosocial behavior, whereas second-born children showed the most favorable patterns, and third-or-later-born children showed lower odds of total difficulties.