Maternal PM2.5 exposure triggers preterm birth: a cross-sectional study in Wuhan, China

Table 1 Characteristics of the study population, by term and preterm births (Wuhan, China, November 1, 2013 to May 31, 2014; January 1, 2015 to August 31, 2015)

Covariates	Preterm births		Term births		p value ^a
Covariates	n	%	n	%	p value ^a
Maternal age, years					0.018
≤ 24	24	18.6	105	81.4
25–29	85	10.5	721	89.5
30–34	73	13.1	486	86.9
≥ 35	91	15.0	516	85.0
Years of education					< 0.001
≤ 9	69	24.8	209	75.2
10–13	62	17.5	293	82.5
≥ 14	142	9.7	1326	90.3
Sex of infant					0.335
Male	151	13.7	954	86.3
Female	122	12.2	874	87.8
Delivery mode					0.030
Vaginal	97	11.1	776	88.9
Cesarean	176	14.3	1050	85.7
Gravidity
1	119	10.0	1076	90.0	< 0.001
≥ 2	154	17.0	752	83.0
Parity					< 0.001
1	183	10.8	1504	89.2
≥ 2	90	21.8	322	78.2
Gestational hypertension					< 0.001
Yes	39	37.1	66	62.9
No	234	11.7	1762	88.3
Gestational diabetes					0.019
Yes	18	21.4	66	78.6
No	255	12.6	1762	87.4
Season conceived					0.045
Warm	169	12.0	1243	88.0
Cold	104	15.1	585	84.9

ISSN: 2397-0642