The impact of high apparent temperature on spontaneous preterm delivery: a case-crossover study

Table 1 Characteristics of the Study Population, by California County, 1995-2009 (N = 14,466)

County	N^a	Maternal Age (years), %				Maternal Race/Ethnicity, %					Infant Sex,%
County	N^a	18-19	20-24	25-34	>35	White	Black	Hispanic	Asian	Other^b	Male
Alameda	2,362	5	17	55	24	27	14	22	26	12	54
Butte^c	24	21	29	38	13	71	0	13	13	4	58
Contra Costa	1,467	5	16	54	24	45	11	18	16	10	55
El Dorado/Amador	95	5	6	66	22	82	0	7	6	4	60
Madera	39	10	21	41	28	38	5	51	3	3	59
Marin	198	2	13	58	27	60	5	21	10	5	51
Merced	17	6	24	35	35	47	0	29	0	24	59
Monterey	17	0	35	41	24	35	0	47	12	6	59
Napa/Lake	166	6	19	54	20	62	0	33	2	2	58
Nevada/Fresno	476	8	22	53	17	43	7	38	9	3	55
Placer	311	5	18	59	18	70	2	13	11	4	50
Sacramento	2,489	8	21	51	20	49	14	17	17	4	56
San Benito	24	4	8	54	33	50	8	38	0	4	63
San Francisco	800	3	13	54	30	30	12	19	34	6	59
San Joaquin	661	7	17	57	19	31	10	33	14	12	55
San Mateo	878	4	15	55	26	30	2	28	34	6	56
Santa Clara	2,441	4	16	57	23	35	3	29	24	9	54
Santa Cruz	18	6	17	33	44	72	0	6	0	22	61
Solano	1,018	8	23	50	19	40	19	16	20	5	54
Sonoma/Mendocino	566	6	17	56	20	67	1	23	6	2	57
Stanislaus	211	3	19	62	16	33	3	30	6	28	48
Sutter	13	8	15	54	23	46	15	23	8	8	62
Tulare/King	17	6	41	35	18	24	0	65	0	12	59
Yolo	158	6	20	56	18	53	3	27	16	1	51
Total	14,466	6	18	54	22	40	9	23	20	8	55

ISSN: 1476-069X