Air pollution in the week prior to delivery and preterm birth in 24 Canadian cities: a time to event analysis

Stieb, David M.; Lavigne, Eric; Chen, Li; Pinault, Lauren; Gasparrini, Antonio; Tjepkema, Michael

doi:10.1186/s12940-018-0440-8

Environmental Health

Table 1 Preterm and term births by maternal and infant characteristics, city, season and year

From: Air pollution in the week prior to delivery and preterm birth in 24 Canadian cities: a time to event analysis

Variable	Number of Births^a			Percent Preterm
Variable	Preterm	Term	Total	Percent Preterm
Maternal age (years)
19 or less	3515	38,690	42,200	8.33
20–29	33,795	501,050	534,845	6.32
30–39	39,760	587,780	627,540	6.34
40+	3800	39,765	43,565	8.72
Missing	10	75	90	11.11
Maternal marital status
Single	18,080	223,090	241,170	7.50
Married	51,410	809,340	860,755	5.97
Widowed	70	965	1035	6.76
Divorced	1050	12,175	13,225	7.94
Separated	330	3345	3675	8.98
Missing	9935	118,450	128,385	7.74
Parity
0	41,025	546,435	587,460	6.98
1	23,890	405,325	429,215	5.57
2	15,775	213,305	229,080	6.89
Missing	190	2300	2490	7.63
Maternal country of birth
Other	33,855	500,350	534,205	6.34
Canada	45,085	642,225	687,310	6.56
Missing	1935	24,790	26,725	7.24
Infant sex
Male	44,380	596,410	640,790	6.93
Female	36,495	570,950	607,445	6.01
Missing	5	5	10	50.00
City
St. John’s	725	8570	9295	7.80
Saint John	455	6760	7215	6.31
Fredericton	335	4620	4955	6.76
Quebec	2630	37,975	40,605	6.48
Trois Rivieres	625	9690	10,315	6.06
Montreal	11,350	170,830	182,180	6.23
Ottawa	5110	76,605	81,715	6.25
Oshawa	855	12,845	13,700	6.24
Toronto	17,395	265,895	283,290	6.14
Mississauga	4340	72,490	76,830	5.65
Brampton	3695	52,325	56,020	6.60
Hamilton	3205	44,960	48,165	6.65
St. Catharines	690	11,390	12,085	5.71
Kitchener	1370	21,600	22,970	5.96
Windsor	1445	21,885	23,330	6.19
Winnipeg	4965	64,845	69,810	7.11
Calgary	8980	111,425	120,405	7.46
Edmonton	6630	78,655	85,285	7.77
Richmond	835	14,630	15,470	5.40
Vancouver	3475	51,610	55,085	6.31
Victoria	375	5805	6180	6.07
Nanaimo	425	6385	6810	6.24
Kamloops	440	6940	7385	5.96
Kelowna	525	8620	9150	5.74
Birth year
1999	7660	113,210	120,875	6.34
2000	7980	113,205	121,185	6.58
2001	7810	115,315	123,130	6.34
2002	7750	113,460	121,210	6.39
2003	6880	100,615	107,495	6.40
2004	8115	115,690	123,805	6.55
2005	8365	118,735	127,100	6.58
2006	8505	122,110	130,615	6.51
2007	8720	125,625	134,340	6.49
2008	9090	129,395	138,485	6.56
Season
Spring (Apr-Jun)	20,725	300,785	321,510	6.45
Summer (Jul-Sep)	20,195	305,135	325,330	6.21
Autumn (Oct-Dec)	19,850	280,030	299,880	6.62
Winter (Jan-Mar)	20,110	281,415	301,525	6.67
Gestation (weeks)
20–27	4590	0	4590	.
28–31	6580	0	6580	.
32–33	8735	0	8735	.
34–36	60,970	0	60,970	.
37+	0	1,167,365	1,167,365	.
Total	80,875	1,167,365	1,248,240	6.48
Total (excluding missing covariates)	63,400	938,300	1,001,700	6.34

^aIn accordance with Statistics Canada disclosure rules, case counts of less than five were suppressed, and all frequencies were randomly rounded to base five. As a result, there may be discrepancies between column totals and totals by infant/maternal characteristic. Statistical analyses employed unrounded data

Back to article page

ISSN: 1476-069X

Contact us

General enquiries: journalsubmissions@springernature.com