. Author manuscript; available in PMC: 2019 Oct 1.

Published in final edited form as: J Dev Behav Pediatr. 2018 Oct-Nov;39(8):601–609. doi: 10.1097/DBP.0000000000000601

Table 1.

Characteristics of children with autism spectrum disorder identified from the Autism and Developmental Disabilities Monitoring Network surveillance years 2008, 2010, and 2012, by advanced maternal age at childbirth.

	Maternal age <35 N=8322		Maternal age ≥35 N=2036

	N	%	N	%	P value^*

Maternal race / ethnicity					<0.001
White	5071	61.1	1399	69.4
Black	1754	21.1	361	17.9
Other	366	4.4	88	4.4
Hispanic	1108	13.4	169	8.4
Missing	23		19
Maternal education (years)					<0.0001
Teen pregnancy	155	1.9	-
<12	1007	12.5	96	4.9
12–<16	4337	53.8	817	41.7
>=16	2557	31.7	1048	53.4
Missing	266		75
Site					<0.0001
AL	220	2.6	31	1.5
AR	571	6.9	66	3.2
AZ	916	11.0	198	9.7
CO	476	5.7	137	6.7
GA	1158	13.9	342	16.8
MD	658	7.9	212	10.4
MO	692	8.3	163	8.0
NC	1035	12.4	254	12.5
NJ	874	10.5	337	16.6
PA	132	1.6	32	1.6
SC	311	3.7	66	3.2
UT	620	7.5	63	3.1
WI	659	7.9	135	6.6
Study year					0.1
2008	1956	23.5	476	23.4
2010	3304	39.7	762	37.4
2012	3062	36.8	798	39.2
Record type					0.3
School	2869	34.5	732	36.0
Health	3306	39.7	775	38.1
Both	2147	25.8	529	26.0
Child Sex					0.8
Male	6870	82.6	1676	82.3
Female	1452	17.4	360	17.7
Birth-order					<0.0001
First born	4200	50.6	669	32.9
Second born	2551	30.7	703	34.5
Third or greater	1557	18.7	664	32.6
Missing	14		-
Plurality					<0.0001
Singleton	7939	95.4	1853	91.0
Multiple	383	4.6	183	9.0
Child gestational age (weeks)					<0.0001
≥37	7099	85.3	1664	81.7
≥35–37	650	7.8	180	8.8
≥32–35	285	3.4	108	5.3
<32	288	3.4	84	4.1
Paternal age					<0.0001^†
Mean, SD	30.1	6.0	38.7	5.5
Missing	1003		133
Age at first evaluation noting developmental concern (mean months, SD)
Overall	44.7	0.2	41.3	0.5	<0.0001^‡
10^th percentile	21.0	0.2	21.0	0.2
20^th percentile	27.0	0.3	26.0	0.5
30^th percentile	31.0	0.2	30.0	0.4
40^th percentile	35.0	0.2	34.0	0.4
50^th percentile	40.0	0.3	37.0	0.6
60^th percentile	47.0	0.4	42.0	0.8
70^th percentile	54.0	0.4	49.0	0.9
80^th percentile	63.0	0.4	59.0	0.8
90^th percentile	75.0	0.4	72.0	0.8
Missing	141		44
Time from first evaluation to first diagnosis (mean months, SD)^{^}
Overall	11.7	0.4	11.5	0.2	0.1^‡
10^th percentile	0.0	0.0	0.0	0.0
20^th percentile	0.0	0.0	0.0	0.0
30^th percentile	0.0	0.0	0.0	0.0
40^th percentile	1.0	0.1	0.0	0.1
50^th percentile	3.0	0.2	3.0	0.4
60^th percentile	8.0	0.3	7.0	0.5
70^th percentile	14.0	0.5	13.0	0.1
80^th percentile	23.0	0.5	23.0	1.1
90^th percentile	37.0	0.7	38.0	1.3
Censored (N, %)	1693	26.3	360	20.9
Missing	141		44

P value calculated by chi-square tests

^†

P value calculated using student t-test

^‡

P value calculated using Wilcoxon test for non-normally distributed continuous data

^{^}

For deciles 10, 20, and 30, all observations were 0