Table 1:

Participant demographic and clinical characteristics, N=398

	ASD (n=171)		DD (n=69)		TD (n=158)
	n	%	n	%	n	%	P-valueg
Sexa							0.03
Male	144	84	48	70	128	81
Female	27	16	21	30	30	19
Race/Ethnicity							0.22
White	90	53	29	42	81	51
Hispanic	53	31	28	41	42	27
Otherb	28	16	12	17	35	22
Season of birthc							0.33
Winter	45	26	19	28	37	23
Spring	30	18	12	17	45	29
Summer	47	27	18	26	35	22
Fall	49	29	20	29	41	26
Birth year							0.02
2000–2001	18	10	2	3	9	6
2002	24	14	17	25	36	23
2003	44	26	22	32	54	34
2004	49	29	20	29	43	27
2005–2006	36	21	8	11	16	10
Maternal education							0.004
High school or less	25	14	22	32	22	14
Some college/Vocational degree	61	36	23	33	48	30
Bachelor’s degree	85	50	24	35	88	56
Maternal allergies or asthmad	103	61	39	57	92	58	0.82
Regional Center catchment areaa							0.45
Alta, Far Northern, and Redwood Coast	71	42	31	45	70	44
North Bay	21	12	6	9	19	12
East Bay, San Andreas, and Golden Gate	44	26	13	19	44	28
Valley Mountain, Central Valley, and selected Southern CA regionsf	35	20	19	27	25	16
	Mean	SD	Mean	SD	Mean	SD	P-valueg
Maternal age at delivery	31.3	5.3	30.9	6.4	31.0	5.4	0.81
Gestational age (weeks)e	39.6	2.1	39.1	2.0	39.3	1.6	0.11
Age (hours) at blood spot collection	29.1	8.8	33.1	8.4	28.7	8.9	0.001
Age (months) at study enrollment for childa	44.0	9.5	46.5	8.7	42.8	10.0	0.03
Years between collection and elution	12.1	1.3	12.2	1.1	12.3	1.1	0.13

^aTD controls were frequency-matched to a projected distribution of ASD cases on age, sex, and regional center catchment area

^bIncludes Black/African American, American Indian/Alaska Native, Asian, Pacific Islander/Native Hawaiian, Multi-racial

^cMonths grouped by season as follows: Winter = December to February, Spring = March to May, Summer = June to August, Fall = September to November

^d1 participant (ASD) was missing maternal allergies/asthma; allergies include the following types: environmental (e.g., seasonal, pet, mold), food, skin, medication, or other

^e2 participants were missing gestational age (1 ASD, 1 TD)

^fSouthern California regions include Los Angeles, Kern, Orange, San Diego, Tri-counties, and Inland

^gP-values for categorical and continuous variables calculated with Chi-square test and one-way analysis of variance (ANOVA), respectively