Relative risk HR for three degrees of preterm birth according to the cumulative daily loads lifted at work in pregnancy
| Degree of preterm birth (full gestational weeks) Number of events | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
| Extremely preterm (22–27) N=110 | Very preterm (28–32) N=415 | Moderately preterm (33–36) N=2.345 | ||||||||
| Loads per day | N | Crude HR | Adjusted* HR | (95% CI) | Crude HR | Adjusted* HR | (95% CI) | Crude HR | Adjusted* HR | (95% CI) |
| No lifting | 46.199 | 1 | 1 | 1 | 1 | 1 | 1 | |||
| 15–50 kg | 5.326 | 1.25 | 1.35 | (0.72 to 0.55) | 0.82 | 0.82 | (0.56 to 1.21) | 0.98 | 0.99 | (0.85 to 1.15) |
| 51–100 kg | 3.396 | 1.24 | 1.42 | (0.65 to 3.10) | 0.82 | 0.84 | (0.52 to 1.36) | 1.10 | 1.13 | (0.95 to 1.35) |
| 101–200 kg | 3.342 | 0.54 | 0.62 | (0.19 to 1.96) | 1.35 | 1.41 | (0.96 to 2.07) | 1.12 | 1.17 | (0.98 to 1.40) |
| 201–500 kg | 3.043 | 1.59 | 1.84 | (0.88 to 3.83) | 1.54 | 1.61 | (1.10 to 2.36) | 1.14 | 1.20 | (1.00 to 1.44) |
| 501–1000 kg | 1.022 | 1.17 | 1.36 | (0.33 to 5.57) | 1.22 | 1.26 | (0.62 to 2.55) | 0.88 | 0.93 | (0.66 to 1.31) |
| >1000 kg | 475 | 3.86 | 4.32 | (1.35 to 13.82) | 1.65 | 1.65 | (0.68 to 4.00) | 1.28 | 1.34 | (0.88 to 2.05) |
62 803 women in the Danish National Birth Cohort 1996–2002.
*Adjusted for maternal age, parity, cervical cone biopsy, IVF/ICSI treatment and smoking.
ICSI, intra-cytoplasmic sperm injection; IVF, in vitro fertilisation.