Table 1.

Selected Characteristics of the Birth Cohort and Children with ASD and ID in Eight North Carolina Counties in 2002, 2004, 2006 and 2008

Variable	Birth Cohort n (%)	All ASD n (%)	ASD-ID n (%)	ASD+ID n (%)	All ID n (%)
Total	11809 (100.00)	561 (100.00)	330 (100.00)	231 (100.00)	1028 (100.00)
Sex
Male	6073 (51.43)	464 (82.71)	279 (84.55)	185 (80.09)	665 (64.69)
Female	5736 (48.57)	97 (17.29)	51 (15.45)	46 (19.91)	363 (35.31)
Year of Birth
1994	2727 (23.09)	87 (15.51)	49 (14.85)	38 (16.45)	224 (21.79)
1996	2825 (23.92)	119 (21.21)	66 (20.00)	53 (22.94)	266 (25.88)
1998	2958 (25.05)	151 (26.92)	86 (26.06)	65 (28.14)	254 (24.71)
2000	3299 (27.94)	204 (36.36)	129 (39.09)	75 (32.47)	284 (27.63)
Maternal Age at Birth
Under 25	4984 (42.21)	184 (32.80)	89 (26.97)	95 (41.13)	460 (44.75)
25-35	5435 (46.02)	281 (50.09)	184 (55.76)	97 (41.99)	465 (45.23)
Over 35	1388 (11.75)	96 (17.11)	57 (17.27)	39 (16.88)	103 (10.02)
Missing	2 (0.02)	0 (0.00)	0 (0.00)	0 (0.00)	0 (0.00)
Maternal Race
White	8148 (69.00)	368 (65.6)	238 (72.12)	130 (56.28)	519 (50.49)
Other	3661 (31.00)	193 (34.4)	92 (27.88)	101 (43.72)	509 (49.51)
Maternal Educational Attainment
Less than High School	2553 (21.62)	76 (13.55)	29 (8.79)	47 (20.35)	377 (36.67)
High School	3424 (29.00)	149 (26.56)	66 (20.00)	83 (35.93)	372 (36.19)
Some College	2472 (20.93)	126 (22.46)	77 (23.33)	49 (21.21)	144 (14.01)
College or More	3341 (28.29)	208 (37.08)	157 (47.58)	51 (22.08)	134 (13.04)
Missing	19 (0.16)	2 (0.36)	1 (0.30)	1 (0.43)	1 (0.10)
Maternal Tobacco Use During Pregnancy
Yes	1647 (13.95)	67 (11.94)	38 (11.52)	29 (12.55)	208 (20.23)
No	10150 (85.95)	493 (87.88)	292 (88.48)	201 (87.01)	819 (79.67)
Missing	12 (0.10)	1 (0.18)	0 (0.00)	1 (0.43)	1 (0.10)
Plurality
Yes	353 (2.99)	23 (4.10)	14 (4.24)	9 (3.90)	54 (5.25)
No	11456 (97.01)	538 (95.90)	316 (95.76)	222 (96.10)	974 (94.75)