Associations of maternal exposure to fine particulate matter with preterm and early-term birth in high-risk pregnant women

Table 1 Characteristics of mothers of preterm and term infants

Characteristics	Total		Preterm birth		Term birth^*		P
	N=7974(100%)		N=652(8.18%)		N=7322(91.82%)
	n	(%)	n	(%)	n	(%)
Maternal age ≥ 35(%)	3909	49.02	329	50.46	3580	48.89	0.47
BMI≥24 (%)	408	5.12	40	6.13	368	5.03	0.25
Exposure to hazardous poison (%)	93	1.17	7	1.07	86	1.17	0.97
Number of previous deliveries (%)							0.01
0	3964	49.71	351	53.83	3613	49.34
1	3908	49.01	288	44.17	3620	49.44
2	102	1.28	13	1.99	89	1.22
Number of previous pregnancies (%)							0.13
0	2351	29.48	197	30.21	2154	29.42
1	2820	35.36	210	32.21	2610	35.65
2	1637	20.53	132	20.25	1505	20.55
≥3	1166	14.62	113	17.33	1053	14.38
Baby’s sex of male (%)	4107	51.50	348	53.37	3759	51.34	0.34
In Vitro Fertilization (%)	763	9.57	72	11.04	691	9.44	0.21
Delivery by cesarean section (%)	4042	50.69	418	64.11	3624	49.49	<0.001
Hyperglycemia (%)	189	2.37	23	3.53	166	2.27	0.06
Hypertension (%)	151	1.89	37	5.67	114	1.56	<0.001
Scarred uterus (%)	2223	27.88	190	29.14	2033	27.77	0.48
Ovarian cyst (%)	186	2.33	16	2.45	170	2.32	0.94
Uterine fibroids (%)	976	12.24	83	12.73	893	12.20	0.74
Season of conception (%)							0.19
Spring	2042	25.61	185	28.37	1857	25.36
Summer	1873	23.49	135	20.71	1738	23.74
Autumn	1934	24.25	153	23.47	1781	24.32
Winter	2125	26.65	179	27.45	1946	26.58
Year of conception (%)							<0.001
2014	22	0.28	0	0.00	22	0.30
2015	1557	19.53	110	16.87	1447	19.76
2016	2723	34.15	225	34.51	2498	34.12
2017	2932	36.77	228	34.97	2704	36.93
2018	740	9.28	89	13.65	651	8.89

ISSN: 1880-7062