Table 2. Associations between Birth Spacing and Autism Spectrum Disorder, Study to Explore Early Development (SEED), United States.

Inter-pregnancy Interval (m)	Total Sample Unadjusted OR (95% CI)	Total Sample, Adjustment for sociodemographics aOR† (95% CI)	Term Birth Sample, Adjustment for sociodemographics aOR† (95% CI)	Term Birth Sample, Adjustment for sociodemographics + maternal report of trying to get pregnant aOR† (95% CI)	Term Birth Sample, Adjustment for sociodemographics + maternal infertility disorder aOR† (95% CI)	Term Birth Sample, Adjustment for sociodemographics + prenatal hypertension, diabetes aOR† (95% CI)
ASD (all)
<12	1.4 (0.97–2.1)	1.3 (0.9–2.0)	1.6 (1.00–2.4)	1.6 (0.99–2.5)	1.6 (1.03–2.6)	1.5 (0.97–2.4)
12–<18	1.2 (0.8–1.8)	1.4 (0.9–2.0)	1.5 (0.98–2.4)	1.4 (0.9–2.2)	1.4 (0.9–2.1)	1.5 (0.95–2.3)
All <18	1.3 (0.97–1.8)	1.3 (0.96–1.9)	1.5 (1.1–2.2)	1.5 (1.03–2.2)	1.5 (1.03–2.2)	1.5 (1.04–2.1)
18–59	Ref	Ref	Ref	Ref	Ref	Ref
≥60	1.8 (1.3–2.6)	1.4 (0.9–2.03)	1.5 (0.99–2.4)	1.7 (1.1–2.6)	1.7 (1.1–2.7)	1.5 (0.97–2.3)

ASD is autism spectrum disorder case group.

^†aOR is adjusted odds ratio, derived from logistic regression models in which the ASD case group is compared to the POP (general population) control group. All models include adjustment for child sex, maternal age at birth, maternal education at birth, and maternal race/ethnicity. Supplemental models additionally adjusted for various potential mediator factors as indicated.