Changes in the number and percentage of births to women with advanced maternal age (≥35 years) before and after policy changes.

Bars indicate the number of births to women with advanced maternal age; the line indicates the percentage. Chi-squared tests with Bonferroni correction were performed in multiple comparisons over years. Significant differences in all pairwise comparisons from 2013 to 2017 were observed; no significant increase in all pairwise comparisons from 2009 to 2013 was found (P < 0.0125, adjusted using Bonferroni correction, 0.05/4 tests).