Table 3.

Maternal Smoking and Autism Spectrum Disorder According to Intellectual Disability Status in the Full Cohort and the Case-Sibling-Cohort^a Births 2007–2010, California.

Smoking Status	With ID				Without ID
	No. of Cases	No. of Noncases	OR b	95% CI	No. of Cases	No. of Noncases	OR b	95% CI
Full cohort
Never smokers	1,144	1,898,355	1.00	Referent	9,891	1,898,355	1.00	Referent
Ever smokersc	51	71,366	1.12	0.84, 1.49	413	71,366	1.15	1.04, 1.27
Prepregnancy smokersd	13	23,952	0.81	0.46, 1.43	159	23,952	1.26	1.07, 1.48
Continued smokerse	37	45,718	1.29	0.92, 1.81	245	45,718	1.09	0.95, 1.24
During pregnancyf, no. of cigarettes/day
1–19	32	40,007	1.27	0.89, 1.82	201	40,007	1.02	0.88, 1.18
≥20	7	8,103	1.42	0.67, 3.01	61	8,103	1.57	1.21, 2.03
Sibling cohorta
Never smokers	259	259	1.00	Referent	2,304	2,256	1.00	Referent
Ever smokersc	13	10	4.62	1.00, 21.44	76	74	0.82	0.50, 1.34
Prepregnancy smokersd	2	2	3.04	0.38, 24.52	24	25	0.87	0.43, 1.77
Continued smokerse	11	7	–g	–g	50	49	0.79	0.43, 1.46
During pregnancyf, no. of cigarettes/day
1–19	7	7	3.87	0.33, 46.10	45	43	0.83	0.45, 1.55
≥20	4	1	–g	– g	8	7	0.89	0.65, 1.53

Abbreviations: CI, confidence interval; ID, intellectual disability; OR, odds ratio.

^a Includes all siblings with at least 1 case among the siblings.

^b Adjusted for birth year, sex, maternal age, maternal race/ethnicity, maternal education, parity, and pregnancy complication.

^c Smoked 3 months before pregnancy or any time during pregnancy.

^d Smoked 3 months before pregnancy but stopped smoking during pregnancy.

^e Smoked 3 months before pregnancy and kept smoking during pregnancy.

^f Smoking was defined as maximum number of cigarettes/day during any trimester.

^g Models did not converge due to distribution of n resulting in small n in some cells.