| Mother’s age (years) | n | % (95% CI) | OR (95% CI) |
| Trent | |||
| <20 | 28 | 12.4 (8.4 to 17.5) | 0.79 (0.52 to 1.29) |
| 20–24 | 62 | 15.1 (11.8 to 19.0) | Reference |
| 25–29 | 68 | 12.0 (9.4 to 15.0) | 0.77 (0.52 to 1.11) |
| 30–34 | 70 | 13.1 (10.3 to 16.3) | 0.85 (0.58 to 1.23) |
| 35–39 | 48 | 17.2 (12.9 to 22.2) | 1.17 (0.77 to 1.77) |
| 40+ | 7 | 12.7 (5.2 to 24.5) | 0.82 (0.35 to 1.90) |
| Total | 284* | 13.6 (12.1 to 15.2) | |
| NSW/ACT | |||
| <20 | 23 | 14.1 (9.1 to 20.5) | 1.30 (0.76 to 2.21) |
| 20–24 | 49 | 11.2 (8.4 to 14.6) | Reference |
| 25–29 | 100 | 13.1 (10.8 to 15.8) | 1.19 (0.82 to 1.72) |
| 30–34 | 99 | 12.5 (10.2 to 15.1) | 1.13 (0.78 to 1.63) |
| 35–39 | 52 | 11.8 (8.9 to 15.2) | 1.06 (0.69 to 1.60) |
| 40+ | 9 | 9.7 (4.5 to 17.6) | 0.85 (0.40 to 1.79) |
| Total | 332 | 12.4 (11.1 to 13.7) |
*One missing mother’s age and not included in rows above.
NSW/ACT, New South Wales/the Australian Capital Territory.