Table 2.
The trend of SRB in the subgroups of maternal age at three stages of Two-Child Policy (22 Hospitals in Hebei Province of China, 2013–2017)
| SRB in subgroup | BTCP | OTCP | UTCP | P |
|---|---|---|---|---|
| < 20 years (SRB) | 1.012 | 1.083 | 1.016 | 0.95 |
| 20–24 years (SRB) | 1.079 | 1.049 | 1.012 b2 | < 0.01 |
| 25–29 years (SRB) | 1.079 | 1.058 | 1.054 b2 | 0.06 |
| 30–34 years (SRB) | 1.110 | 1.049 b1 | 1.049 b2 | 0.01 |
| ≥35 years (SRB) | 1.146 | 1.016 b1 | 1.062 b2 | 0.10 |
| Unadjusted OR (95% CI) | ||||
| < 20 years | 1.00 | 1.07(0.91–1.25) | 1.01(0.86–1.17) | 0.67 |
| 20–24 years | 1.00 | 0.97(0.93–1.01) | 0.94(0.89–0.98) | < 0.01 |
| 25–29 years | 1.00 | 0.98(0.95–1.01) | 0.97(0.95–1.00) | 0.13 |
| 30–34 years | 1.00 | 0.95(0.91–0.99) | 0.95(0.91–0.98) | 0.02 |
| ≥ 35 years | 1.00 | 0.80(0.82–0.95) | 0.93(0.87–0.99) | < 0.01 |
| Adjusted OR (95% CI) | ||||
| < 20 years | 1.00 | 1.08(0.92–1.26) | 1.02(0.87–1.19) | 0.65 |
| 20–24 years | 1.00 | 0.98(0.94–1.02) | 0.94(0.90–0.98) | 0.01 |
| 25–29 years | 1.00 | 0.98(0.95–1.01) | 0.97(0.95–0.99) | 0.12 |
| 30–34 years | 1.00 | 0.94 (0.90–0.99) | 0.94(0.90–0.98) | < 0.01 |
| ≥ 35 years | 1.00 | 0.89(0.82–0.96) | 0.93(0.87–0.99) | < 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 was used to examine the strength of association between the SRB and the Two-Child Policy, was showed in Unadjusted OR (95% CI); After adjusting the factors such as delivery mode, parity, maternal education, delivery hospital, multivariate logistic regression analysis was used, and was showed in Adjusted OR (95% CI)
b1Statistically significant when BTCP compared to OTCP;
b2Statistically significant when BTCP compared to UTCP