Characteristics of all singleton births in Sydney from 1998 to 2000 by “small for gestational age”
| Variable | Small for gestational age (n = 13 402) | Not small for gestational age (n = 138 056) | Adjusted OR (95% CI) | ||
|---|---|---|---|---|---|
| No. | % | No. | % | ||
| *Referent group. | |||||
| OR, odds ratio adjusted for other covariates; SD, standard deviation; SES, socioeconomic status. | |||||
| Note that in Australia, autumn is in March, April, May; winter is in June, July, August; spring is in September, October, November; and summer is in December, January, February. | |||||
| Maternal age (years) | |||||
| <24 | 2762 | 20.6 | 19460 | 14.1 | 1.02 (0.97 to 1.08) |
| 25–34* | 8340 | 62.2 | 93828 | 68.0 | 1.00 |
| 35–44 | 2285 | 17.0 | 24639 | 17.8 | 1.01 (0.95 to 1.01) |
| >45 | 15 | 0.1 | 129 | 0.1 | 1.55 (0.84 to 2.84) |
| Maternal smoker | |||||
| Yes | 2659 | 19.8 | 14254 | 10.3 | 1.97 (1.87 to 2.08) |
| No | 10741 | 80.1 | 110375 | 79.9 | |
| Sex of infant | |||||
| Female | 6456 | 48.2 | 60381 | 43.7 | 1.01 (0.97 to 1.05) |
| Male | 6946 | 51.8 | 64273 | 46.6 | |
| Maternal Aboriginality | 0.0 | 0.0 | |||
| Yes | 117 | 0.9 | 806 | 0.6 | 1.03 (0.83 to 1.28) |
| No | 13275 | 99.1 | 123758 | 89.6 | |
| Gestation at first antenatal visit | |||||
| >20 weeks | 1803 | 13.5 | 13854 | 10.0 | 1.12 (1.05 to 1.18) |
| ⩽20 weeks | 11486 | 85.7 | 110014 | 79.7 | |
| Previous pregnancy | |||||
| No | 7427 | 55.4 | 53102 | 38.5 | 0.57 (0.54 to 0.59) |
| Yes | 5973 | 44.6 | 71517 | 51.8 | |
| IRSD quintile | |||||
| 5 (least disadvantaged; high SES)* | 3843 | 28.7 | 58638 | 42.5 | 1.00 |
| 4 | 2857 | 21.3 | 27395 | 19.8 | 1.24 (1.17 to 1.13) |
| 3 | 2374 | 17.7 | 19997 | 14.5 | 1.38 (1.30 to 1.46) |
| 2 | 1684 | 12.6 | 13826 | 10.0 | 1.50 (1.41 to 1.61) |
| 1 (most disadvantaged; low SES) | 2644 | 19.7 | 18200 | 13.2 | 1.73 (1.63 to 1.83) |
| Season of birth | |||||
| Summer (Dec–Feb)* | 3265 | 24.4 | 43727 | 31.7 | 1.00 |
| Autumn (Mar–May) | 3456 | 25.8 | 31109 | 22.5 | 1.05 (0.99 to 1.11) |
| Winter (Jun–Aug) | 3375 | 25.2 | 31469 | 22.8 | 1.00 (0.95 to 1.06) |
| Spring (Sep–Nov) | 3306 | 24.7 | 31751 | 23.0 | 0.99 (0.94 to 1.05) |