Characteristics of 7405 women born preterm and 16 714 born at term, at the time of their birth and during the study period, by their gestational age
| Characteristic | Women’s gestational age; no. (%) of women* | p value | ||
|---|---|---|---|---|
| < 32 wk n = 554 | 32–36 wk n = 6851 | Term, 37–42 wk n = 16 714 | ||
| At birth | ||||
| Mother’s age, yr | ||||
| < 18 | 27 (4.9) | 196 (2.9) | 323 (1.9) | < 0.001 |
| ≥ 25 | 266 (48.0) | 3661 (53.4) | 9491 (56.8) | < 0.001 |
| Mean ± SD | 24.8 ± 5.1 | 25.3 ± 4.8 | 25.4 ± 4.6 | < 0.001 |
| Mother’s education < 12 yr† | 332 (62.9) | 4001 (62.0) | 9019 (55.7) | < 0.001 |
| Mother’s first delivery (v. second or more) | 251 (45.3) | 3090 (45.1) | 7101 (42.5) | < 0.001 |
| Multiple birth | 57 (10.3) | 513 (7.5) | 1 245 (7.4) | 0.04 |
| Gestational age, wk, median (IQR) | 30 (29–31) | 36 (34–36) | 40 (39–40) | < 0.001 |
| Birth weight, g, mean ± SD | 1500 ± 504 | 2482 ± 543 | 3199 ± 490 | < 0.001 |
| Small for gestational age | 48 (8.7) | 1002 (14.6) | 2498 (14.9) | < 0.001 |
| Born < 1980 | 265 (47.8) | 3519 (51.4) | 9012 (53.9) | < 0.001 |
| During study period | ||||
| Parity, no. of live births | 0.14 | |||
| 1 | 304 (54.9) | 3476 (50.7) | 8350 (50.0) | |
| 2 | 186 (33.6) | 2527 (36.9) | 6187 (37.0) | |
| ≥ 3 | 64 (11.6) | 848 (12.4) | 2 177 (13.0) | |
| Stillbirth delivery | 6 (1.1) | 36 (0.5) | 89 (0.5) | 0.22 |
| At first live delivery | n = 517 | n = 6405 | n = 15 978 | |
| Age, yr | ||||
| < 18 | 32 (6.2) | 417 (6.5) | 873 (5.5) | 0.009 |
| ≥ 25 yr | 203 (39.3) | 2456 (38.3) | 6490 (40.6) | 0.007 |
| Mean ± SD | 23.1 ± 3.7 | 23.1 ± 3.8 | 23.4 ± 3.8 | < 0.001 |
| Education < 12 yr† | 212 (44.6) | 2466 (41.7) | 5340 (36.0) | < 0.001 |
| Multiple birth | < 5‡ | 26 (0.4) | 86 (0.5) | 0.12 |
Note: IQR = interquartile range, SD = standard deviation.
↵* Unless stated otherwise.
↵† Data on education levels were available for 23 163 (96%) of the mothers at the time of the women’s birth and for 21 209 (88%) of the women at the time of their first delivery.
↵‡ Numbers less than 5 are not reported, to respect confidentiality.