Table 1.
Characteristics of mothers and preterm births in Brisbane, Australia, 2009–2013.
| Variables | n (%) |
|---|---|
| Total | 6949 (100.0) |
| Maternal age (years) | |
| < 35 | 5260 (75.7) |
| ≥ 35 | 1689 (24.3) |
| Prepregnancy medical conditions | |
| No | 5122 (73.7) |
| Yes | 1827 (26.3) |
| Previous pregnancy | |
| 0 | 2514 (36.2) |
| ≥ 1 | 4435 (63.8) |
| Maternal smoking status | |
| Smokers | 773 (11.1) |
| Nonsmokers | 6176 (88.9) |
| Number of births | |
| Single | 4929 (70.9) |
| Multiple | 2020 (29.1) |
| Infant sex | |
| Female | 3276 (47.1) |
| Male | 3673 (52.9) |
| SES index | |
| Index 1–5 (low level) | 910 (13.1) |
| Index 6–10 (high level) | 6039 (86.9) |