TABLE 1.

Percent Distribution of Children With Autism Spectrum Disorders and Speech and Language Impairment Born Inside the Surveillance Regions of the Autism and Developmental Disabilities Monitoring Network by Characteristics of the Child, Family, Census Tract, and Surveillance Year

	North Carolina		West Virginia
	Autism Spectrum Disorders (n = 206) %	Speech and Language Impairment (n = 1733) %	Autism Spectrum Disorders (n = 189) %	Speech and Language Impairment (n = 1146) %
Child characteristics
Sex
Girl	13	36	24	35
Boy	87	64	76	65
Race
Non-Hispanic white	58	64	95	97
Non-Hispanic black	36	28	4	3
Other	7	7	1	1
First born
No	47	65	54	64
Yes	53	35	46	36
Previously diagnosed autism
Yes	77		72
No	23		28
Comorbid intellectual disabilities
Yes (IQ ≤70)	44		37
No	50		30
Missing	5		33
Family characteristics
Maternal education
<High school	15	23	17	26
High school degree	51	56	68	65
College degree	35	21	15	9
Maternal age (years)
≤22	18	25	26	35
23–34	68	62	62	56
≥35	14	13	12	8
Married
No	29	31	27	27
Yes	71	69	73	73
Smoking in pregnancy
No	87	81	75	71
Yes	13	19	25	29
Census tract characteristics
Urban/rural
100% Rural	10	17	40	46
Mixed	50	47	43	42
100% Urban	39	35	18	12
Median household income ($/year)
≤20,000	12	14	47	50
20,001 ≤ 30,000	44	43	37	40
30,001 ≤ 40,000	26	33	15	10
>40,000	17	11	1	1
Study design
Surveillance year
2000	0	0	43	53
2002	42	53	57	47
2004	58	47	0	0