Table 1_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.docx

No significant associations were found for total difficulties (OR = 0.97, p = 0.600) or internalizing problems (OR = 0.99, p = 0.880). Further analyses by birth order revealed that, compared with only children, second-born children showed modestly lower odds of total difficulties (OR = 0.65, 95% CI: 0.51–0.84, p = 0.001) and internalizing problems (OR = 0.75, 95% CI: 0.59–0.96, p = 0.019). Third-or-later-born children also exhibited a reduced risk of total difficulties (OR = 0.61, 95% CI: 0.38–0.98, p = 0.037).

Conversely, first-born children were at increased risk of externalizing problems (OR = 1.30, 95% CI: 1.02–1.65, p = 0.034) and demonstrated lower prosocial behavior (OR = 0.82, 95% CI: 0.67–1.00, p = 0.048) compared to only children. Sensitivity analyses largely corroborated these findings, and no interactions remained significant after FDR correction (all q > 0.05).</p>Conclusion<p>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.</p>