| Age period | ASD cases (n) | Rest of cohort (n) | OR (95% CI) | p Value |
| 0–4 weeks | 2.7% (2) | 3.2% (392) | 0.82 (0.20 to 3.36) | 0.784 |
| 0–6 months | 33.3% (23) | 33.4% (3808) | 0.98 (0.59 to 1.62) | 0.934 |
| 6–18 months | 50.0% (37) | 51.3% (5637) | 0.91 (0.58 to 1.44) | 0.697 |
| 18–30 months | 56.3% (40) | 55.1% (5648) | 0.98 (0.61 to 1.57) | 0.925 |
| 30–42 months | 57.6% (38) | 44.0% (4396) | 1.68 (1.03 to 2.74) | 0.039 |
Odds ratios are relevant to children with no history of diarrhoea in the particular period, after taking account of the sex of the child. ASD, autistic spectrum disorder.