Table 1.

Distribution of Selected Characteristics of the Study Population (n = 10,094), Urban China, 2010–2012

Characteristic	Preterm Birth (n = 1,009)		Full-Term Birth (n = 9,085)		P Valuea
	No.	%	No.	%
Age, years					<0.0001
<25	239	23.7	1,383	15.2
25–29	361	35.8	4,452	49.0
≥30	409	40.5	3,250	35.8
Education, years					<0.0001
≤9	392	39.7	1,835	20.6
10–15	373	37.8	3,556	39.8
≥16	222	22.5	3,532	39.6
Missing	22		162
Employment status					<0.0001
No	593	58.8	4,287	47.2
Yes	416	41.2	4,798	52.8
Parity					<0.0001
Nulliparous	623	61.7	6,751	74.3
Parous	386	38.3	2,334	25.7
History of preterm delivery					<0.0001
No	962	95.3	9,053	99.6
Yes	47	4.7	32	0.4
Preeclampsia					<0.0001
No	876	86.8	8,887	97.8
Yes	133	13.2	198	2.2
Diabetes					0.024
Yes	992	98.3	9,000	99.1
No	17	1.7	85	0.9
Prepregnancy body mass indexb					0.025
≤18.5	192	20.2	1,863	21.2
18.6–23.9	629	66.2	5,996	68.1
≥24	129	13.6	941	10.7
Missing	59		285
Alcohol drinking during pregnancy					0.81
No	1,007	99.8	9,070	99.8
Yes	2	0.2	15	0.2
Cesarean delivery					<0.0001
No	482	49.8	5,680	63.0
Yes	486	50.2	3,334	37.0
Missing	41		71
Sex of the child					0.15
Boy	551	54.9	4,761	52.6
Girl	452	45.1	4,297	47.4
Missing	6		27

^a The analysis did not account for missing data.

^b Weight (kg)/height (m)².