Table 2.
Association between month of birth and autism before 6 years of age. California births 1990 – 2002.
| Month of birth | Unadjusted model OR (95% CI) | Model 3a OR (95% CI) | Model 4b OR (95% CI) |
|---|---|---|---|
| January | 0.97 (0.90 – 1.04) | 0.98 (0.91 – 1.05) | 1.01 (0.94 – 1.08) |
| February | 0.98 (0.91 – 1.05) | 0.99 (0.92 – 1.06) | 1.01 (0.94 – 1.09) |
| March | 0.97 (0.91 – 1.05) | 0.98 (0.91 – 1.05) | 0.99 (0.92 – 1.06) |
| Aprilc | 1.00 | 1.00 | 1.00 |
| May | 1.03 (0.96 – 1.11) | 1.03 (0.96 – 1.10) | 1.02 (0.95 – 1.09) |
| June | 1.03 (0.96 – 1.11) | 1.03 (0.96 – 1.11) | 1.01 (0.94 – 1.09) |
| July | 1.06 (0.99 – 1.14) | 1.07 (1.00 – 1.15) | 1.04 (0.97 – 1.12) |
| August | 1.07 (1.00 – 1.15) | 1.09 (1.01 – 1.16) | 1.04 (0.97 – 1.12) |
| September | 1.10 (1.02 – 1.17) | 1.11 (1.04 – 1.19) | 1.06 (0.99 – 1.13) |
| October | 1.10 (1.02 – 1.17) | 1.11 (1.04 – 1.20) | 1.04 (0.97 – 1.12) |
| November | 1.18 (1.10 – 1.27) | 1.20 (1.12 – 1.29) | 1.12 (1.04 – 1.20) |
| December | 1.10 (1.03 – 1.18) | 1.12 (1.04 – 1.20) | 1.04 (0.97 – 1.12) |
a
Model 3 adjusted for maternal education, child ethnicity, and year of birth as a categorical variable.
b
Model 4 adjusted for maternal education, child ethnicity, and year of birth as a continuous variable.
c
Reference category.