Table 3.

Association between universal two-child policy and early-term birth stratified by maternal age, previous uterine scars and parity(n=28 966)

Adjusted variables	Crude RR* (95% CI)	P value	Adjusted RR† (95% CI)	P value
Maternal age
<30	1.22 (1.16 to 1.28)	<0.0001	1.24 (1.18 to 1.30)	<0.0001
30–34	1.15 (1.08 to 1.22)	<0.0001	1.14 (1.07 to 1.22)	<0.0001
≥35	1.06 (0.97 to 1.15)	0.1816	1.05 (0.97 to 1.15)	0.2241
Previous uterine scars
No	1.20 (1.16 to 1.25)	<0.0001	1.21 (1.16 to 1.26)	<0.0001
Yes	1.08 (1.02 to 1.15)	0.0104	1.08 (1.01 to 1.15)	0.0263
Parity
Nulliparous	1.18 (1.12 to 1.24)	<0.0001	1.19 (1.13 to 1.26)	<0.0001
Multiparous	1.20 (1.14 to 1.25)	<0.0001	1.17 (1.12 to 1.23)	<0.0001

*Not adjusted for any variables.

†Adjusted for maternal sociodemographic status, maternal health conditions and newborn’s characteristic.

‡Adjusted for maternal sociodemographic status.

§Adjusted for maternal health conditions.

¶Adjusted for newborn’s characteristics.

RR, relative risk.