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| Fracture group | Fusion surgery group | Control group | ||||
|---|---|---|---|---|---|---|
| Total number | 2301 | 632 | 1 154 469 | |||
| n | % | n | % | n | % | |
| Age at birth (years, mean SD) | 29.4 (4.7) | 30.6 (6.2) | 29.7 (5.4) | |||
| Nulliparous | 1060 | 46.1 | 274 | 43.4 | 477 595 | 41.4 |
| Previous C-section | 241 | 10.5 | 99 | 15.7 | 124 013 | 10.7 |
| Smoking during pregnancy | 625 | 27.2 | 114 | 18.0 | 168 633 | 14.6 |
