Table 1. Pregnancy characteristics of 77,327 women according to induction of labour.
| Characteristic | Group | Not induced (n = 51,744) n (%) |
Induced (n = 25,583) n (%) |
Total n (%) |
|---|---|---|---|---|
| Maternal age (years) | 35–39 | 43,691 (84.4) | 19,880 (77.7) | 63,571 (82.2) |
| 40–50 | 8,053 (15.5) | 5,703 (22.3) | 13,756 (17.8) | |
| Maternal ethnicity* | White | 37,507 (80.1) | 19,341 (82.7) | 56,848 (81.0) |
| Asian | 3,352 (7.2) | 1,453 (6.2) | 4,805 (6.8) | |
| Black | 2,655 (5.7) | 1,224 (5.2) | 3,879 (5.5) | |
| Other | 3,319 (7.1) | 1,357 (5.8) | 4,676 (6.7) | |
| Maternal SES quintile | SES 1 (least deprived) | 11,350 (21.9) | 5,565 (21.8) | 16,915 (21.9) |
| SES 2 | 10,861 (21.0) | 5,444 (21.3) | 16,305 (21.1) | |
| SES 3 | 10,470 (20.2) | 5,190 (20.3) | 15,660 (20.3) | |
| SES 4 | 11,225 (21.7) | 5,492 (21.5) | 16,717 (21.6) | |
| SES 5 (most deprived) | 7,836 (15.1) | 3,890 (15.2) | 11,726 (15.2) | |
| Year of birth | 2009 | 11,897 (23.0) | 5,147 (20.1) | 17,044 (22.0) |
| 2010 | 10,732 (20.7) | 5,001 (19.6) | 15,733 (20.4) | |
| 2011 | 10,756 (20.8) | 5,348 (20.9) | 16,104 (20.8) | |
| 2012 | 9,545 (18.5) | 5,193 (20.3) | 14,738 (19.1) | |
| 2013 | 8,814 (17.0) | 4,894 (19.1) | 13,708 (17.8) | |
| Birthweight centile | 10–90th | 43,538 (84.1) | 21,164 (82.7) | 64,702 (83.7) |
| <10th | 4,545 (8.8) | 2,597 (10.2) | 7,142 (9.2) | |
| >90th | 3,661 (7.1) | 1,822 (7.1) | 5,483 (7.1) | |
| Sex of baby | Male | 21,311 (50.9) | 13,245 (51.8) | 39,556 (51.2) |
| Pregnancy complications | Preeclampsia | 2,493 (4.8) | 3,319 (13.0) | 5,812 (7.5) |
| Gestational diabetes | 875 (1.7) | 1,440 (5.6) | 2,315 (3.0) | |
| Abnormal fluid volume | 240 (0.5) | 417 (1.6) | 657 (0.9) |
* Ethnicity was unknown in 7,119 (9.2%) of records. A missing category was included in the regression models.
Abbreviations: SES, socioeconomic status.