Crude ORs (95% CI) and P values for the association between birth policy changes and prevalence of BD subtypes with significant changes in total births (in 2013, 2015, and 2017).

ORs and 95% CIs were calculated from exposures (policy changes) and cases (BDs), with 2013 being defined as the reference group. P values were derived from chi-squared tests. Abbreviations: CHD, congenital heart defect; CI, confidence interval; OR, odds ratio.