Table 1.

Associations of maternal and child characteristics with risk of ASD

Characteristics	No. With ASD/Total	Hazard Ratio (95% CI)a
Maternal
Age (per year)		1.03 (1.02–1.04)
Parityb
0	1,123 / 96,964	1.00 (Reference)
1	802 / 78,494	0.87 (0.79–0.95)
≥2	511 / 66,837	0.65 (0.58–0.73)
Educationb
High school or lower	811 / 101,770	1.00 (Reference)
Some college	761 / 68,729	1.33 (1.19–1.48)
College graduate or higher	888 / 73,699	1.31 (1.17–1.46)
Household annual incomeb,c
<$30,000	223 / 20,069	1.32 (1.12–1.57)
$30,000-$49,999	845 / 82,638	1.00 (Reference)
$50,000-$69,999	810 / 78,926	0.91 (0.82–1.02)
$70,000-$89,999	365 / 39,758	0.77 (0.67–0.89)
≥$90,000	228 / 25,029	0.70 (0.59–0.82)
Race/ethnicity
Non-Hispanic white	569 / 62,774	1.00 (Reference)
Non-Hispanic black	266 / 23,855	1.09 (0.92–1.30)
Hispanic	1,216 / 126,123	0.95 (0.85–1.07)
Asian/Pacific Islander	374 / 29,774	1.13 (0.98–1.31)
Other	46 / 3,894	1.26 (0.90–1.74)
History of comorbidityd
No	2,170 / 224,366	1.00 (Reference)
Yes	301 / 22,054	1.32 (1.15–1.51)
Child
Female	441 / 120,112	1.00 (Reference)
Male	2,030 / 126,308	4.77 (4.28–5.32)

^aSpecified family as a random effect, and birth year and KPSC medical center service areas were adjusted as covariates.

^bHazard ratios not reported for children with missing data categories in these variables.

^cBased on census tract median

^d≥1 diagnosis of heart, lung, kidney, or liver disease; cancer in mothers