Table 5.

The trend of SRB in the subgroup of material education at the three stages of Two-Child Policy (22 Hospitals in Hebei Province of China, 2013–2017)

SRB in subgroup	BTCP	OTCP	UTCP	P
College and above (SRB)	1.041	1.032	1.024	0.30
Middle school (SRB)	1.096	1.058 b1	1.058 b2	< 0.01
Primary school and below (SRB)	1.137	1.070	1.062	0.27
Unadjusted OR (95% CI)
College and above	1.00	0.99(0.95–1.03)	0.98(0.95–1.02)	0.58
Middle school	1.00	0.96(0.94–0.99)	0.96(0.94–0.99)	< 0.01
Primary school and below	1.00	0.94(0.83–1.07)	0.93(0.82–1.06)	0.49
Adjusted OR (95% CI)
College and above	1.00	0.99(0.96–1.03)	0.98(0.95–1.01)	0.46
Middle school	1.00	0.96(0.93–0.98)	0.95(0.93–0.98)	< 0.01
Primary school and below	1.00	0.90(0.79–1.03)	0.90(0.79–1.03)	0.21

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 Two-Child Policy stages. BTCP acted as a control, univariate logistic regression was used to examine the strength of association between the SRB and the Two-Child Policy, and was showed in Unadjusted OR (95% CI); After adjusting the factors such as maternal age, delivery mode, parity, 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