Table 1.
Characteristics of the study participants (n = 797,056)
| Women with term birth (n = 737,493) n (%) | Women with preterm birth (n = 59,563) n (%) | |
|---|---|---|
| Age group | ||
| <20 | 19,146 (2.6) | 1,635 (2.7) |
| 20-34 | 524,443 (71.1) | 40,334 (67.8) |
| ≥35 | 193,904 (26.3) | 17,594 (29.5) |
| Country of birth | ||
| Other | 56,046 (7.6) | 4,348 (7.3) |
| Asia | 110,122 (14.9) | 7,526 (12.6) |
| Australia/NZ | 515,753 (69.9) | 44,122 (74.1) |
| Europe/North America | 55,572 (7.6) | 3,567 (6.0) |
| SEIFA index | ||
| 1st quintile (most advantaged) | 145,600 (19.7) | 9,761 (16.4) |
| 2nd quintile | 137,434 (18.6) | 10,205 (17.2) |
| 3rd quintile | 152,245 (20.6) | 12,831 (21.5) |
| 4th quintile | 147,983 (20.2) | 12,475 (20.9) |
| 5th quintile (most disadvantaged) | 154,231(20.9) | 14,291 (24.0) |
| Number of births | ||
| 1 | 220,409 (29.9) | 13,284 (22.3) |
| 2 | 291,368 (39.5) | 21,461 (36.0) |
| ≥3 | 225,716 (30.6) | 24,818 (41.7) |
| Smoking during pregnancy | ||
| Never | 602,684 (81.7) | 41,683 (70.0) |
| Smoking before last pregnancy | 26,914 (3.7) | 4,308 (7.2) |
| Smoking during last pregnancy | 107,895 (14.6) | 13,572 (22.8) |
| Gestational diabetes | ||
| Never | 690,275 (93.6) | 54,163 (90.9) |
| Ever | 47,218 (6.4) | 5,400 (9.1) |
| Diabetes | ||
| No | 734,281 (99.6) | 58,768 (98.7) |
| Yes | 3,212 (0.4) | 795 (1.3) |
| Having a fetal death | ||
| Never | 734,399 (99.6) | 53,539 (89.9) |
| Ever | 3,094 (0.4) | 6,024 (10.1) |
| Having an SGA infant | ||
| Never | 631,749 (85.7) | 48,769 (81.9) |
| 3- <10th percentiles | 75,580 (10.2) | 7,131 (12.0) |
| <3rd percentiles | 30,164 (4.1) | 3,663 (6.1) |