Associations of preterm delivery with occupational activities
| Occupational activity | 11 weeks of gestation | 19 weeks of gestation | 34 weeks of gestation | ||||||
| No exposed (%) | No exposed cases | OR* (95% CI) | No exposed (%) | No exposed cases | OR* (95% CI) | No exposed (%) | No exposed cases | OR* (95% CI) | |
| Worked ⩾40 h/week | 244 (19) | 10 | 1.03 (0.49 to 2.15) | 236 (18) | 9 | 1.01 (0.47 to 2.17) | 130 (16) | 3 | 0.59 (0.17 to 2.03) |
| Standing or walking >4 h/day in total | 484 (37) | 16 | 0.92 (0.49 to 1.70) | 432 (34) | 12 | 0.76 (0.39 to 1.49) | 201 (24) | 6 | 0.99 (0.39 to 2.51) |
| Kneeling/squatting >1 h/day in total | 219 (17) | 6 | 0.77 (0.32 to 1.84) | 209 (16) | 6 | 0.86 (0.36 to 2.06) | 82 (10) | 3 | 1.25 (0.37 to 4.28) |
| Trunk bent forward for >1 h/day in total | 589 (45) | 23 | 1.25 (0.69 to 2.26) | 569 (44) | 23 | 1.47 (0.80 to 2.71) | 315 (39) | 16 | 2.92 (1.27 to 6.70) |
| Lifting weights of ⩾25 kg by hand | 121 (9) | 3 | 0.69 (0.21 to 2.26) | 83 (6) | 3 | 1.10 (0.33 to 3.63) | 24 (3) | 1 | – |
| Night shifts | 131 (10) | 5 | 1.14 (0.43 to 2.93) | 116 (9) | 4 | 1.07 (0.37 to 3.05) | 33 (4) | 2 | – |
*Each risk factor was examined in a separate logistic regression model with adjustment for primiparity. Risk estimates are for those exposed to the risk factor relative to those who were in work at the relevant stage of pregnancy but unexposed.