The effect of an older sibling on the risk of injury, by birth interval
| Birth interval (years) | No (%) with no injury | No (%) with injury | Adjusted odds ratio* (95% CI) |
|---|---|---|---|
| *Adjusted for maternal age. | |||
| No older sibling (n=4589) | 3517 (77) | 1072 (23) | 1.0 |
| <2 (n=1728) | 1172 (68) | 556 (32) | 1.64 (1.44 to 1.85) |
| 2–4 (n=2621) | 1855 (71) | 766 (29) | 1.46 (1.30 to 1.64) |
| >4 (n=1779) | 1264 (71) | 515 (29) | 1.43 (1.25 to 1.64) |
| Unknown (n=799) | 563 (70) | 236 (30) | 1.47 (1.24 to 1.75) |