SRB in subgroup | BTCP | OTCP | UTCP | P |
|---|
 Nulliparous (SRB) | 1.033 | 1.016 | 1.016 | 0.31 |
 Multiparous (SRB) | 1.165 | 1.088 | 1.070 | < 0.01 |
Unadjusted OR (95% CI) |
 Nulliparous | 1.00 | 0.99(0.96–1.01) | 0.99(0.96–1.01) | 0.51 |
 Multiparous | 1.00 | 0.93(0.91–0.96) | 0.92(0.89–0.94) | < 0.01 |
Adjusted OR (95% CI) |
 Nulliparous | 1.00 | 0.99(0.96–1.02) | 0.99(0.97–1.02) | 0.74 |
 Multiparous | 1.00 | 0.94(0.91–0.96) | 0.92(0.90–0.95) | < 0.01 |
- BTCP: Both the husband and wife of one couple were the only child of their parents, the couple were allowed to have Two Children in Policy (January 1, 2013 - May 29, 2014); OTCP: only the husband or wife of one couple was the only child of their parents, the couple were allowed to have Two Children in Policy (May 30, 2014 - December 31, 2015); UTCP: the Universal Two-Child Policy, every couple were allowed to have two children (January 1, 2016 - December 31, 2017). SRB: Sex Ratio at Birth (n (male) / n (female)); OR Odds Ratio; 95% CI: 95% Confidence Intervals
- A chi-square test was used in the SRB at the three stages of Two-Child Policy. BTCP acted as a control, univariate logistic regression analysis was used to examine the strength of association between the SRB and the population policy, showed in Unadjusted OR (95% CI); After adjusting the factors such as maternal age, delivery mode, maternal education, delivery hospital, multivariate logistic regression analysis was used, and was showed in Adjusted OR (95% CI)
