Summary of findings of studies included in meta-analysis for spontaneous abortion
| Report | Exposure | Developed countries and study period >1975 | Response rate ≥80% | Prospective assessment of exposure | Quantitative definition of lifting (weight/frequency) | Adequate control of personals factors | Adequate control of other occupational exposures | Validity score | Risk estimates (95% CI)* |
| (1) Light lifting or <12 kg | |||||||||
| Ahlborg et al 19 | <12 kg, ≥10x/wk | · | · | · | · | · | 15.00 | 0.97 (0.53 to 1.78) | |
| McDonald et al 22 | None or light weight lifting | · | · | · | 10.00 | 0.92 (0.89 to 0.95)† | |||
| (2) Lifting unspecified weight or ≥5 kg | |||||||||
| Ahlborg et al 19 | Any weight,<10x /wk | · | · | · | · | 14.00 | 1.03 (0.70 to 1.53) | ||
| El-Metwalli et al 54 | Lifting | · | 7.00 | 2.04 (1.66 to 2.49) | |||||
| Eskenazi et al 55 | >6.8 kg, ≥1x/d | · | · | · | 11.50 | 1.14 (0.64 to 2.03)‡ | |||
| Fenster et al 56 | >6.8 kg, ≥1x/d | · | · | · | · | 14.50 | 0.97 (0.47 to 2.00)‡ | ||
| Florack et al 43 | Lifting ≥1 hourx/d | · | · | · | · | 13.00 | 1.07 (0.34 to 3.35) | ||
| Lee and Jung57 | >5 kg | 8.00 | 3.39 (2.06 to 5.60) | ||||||
| McDonald et al 22 | Medium weight lifting | · | · | · | · | 10.00 | 1.11 (1.03 to 1.20)† | ||
| Swan et al 58Gr.1§ | >6.8 kg | · | · | · | 13.00 | 1.40 (0.78 to 2.60) | |||
| Swan et al 58Gr.2¶ | >6.8 kg | · | · | · | 13.00 | 1.10 (0.46 to 2.90) | |||
| Swan et al 58Gr.3** | >6.8 kg | · | · | · | 13.00 | 1.50 (0.84 to 2.80) | |||
| (3) Heavy lifting or ≥10 kg−≤10x per day (≤50x/wk) or rarely | |||||||||
| Ahlborg et al 19 | ≥12 kg, 10–50x/wk | · | · | · | · | · | 15.00 | 1.11 (0.77 to 1.58) | |
| Axelsson et al 20 | ≥10 kg, ≤50x/wk | · | · | · | 10.00 | 0.89 (0.67 to 1.18)†† | |||
| Hansteen et al 59 | Heavy lifting, daily or weekly | · | · | 9.00 | 1.40 (1.04 to 1.88)‡‡ | ||||
| Juhl et al
21
(SA<13 wk) | 11–20 kg or >20 kg, 1–10x/d | · | · | · | · | 11.75 | 1.08 (0.85 to 1.38)§§ | ||
| Juhl et al
21
(SA 13–21 wk) | 11–20 kg or >20 kg, 1–10x/d | · | · | · | · | 11.75 | 1.02 (0.79 to 1.31)§§ | ||
| Lerman et al 27 | Heavy lifting, 5–25x/wk | · | 7.00 | 0.47 (0.31 to 0.71) | |||||
| Taskinen et al 23 | ≥10 kg, seldom | · | 10.25 | 1.3 (0.4 to 3.9) | |||||
| Taskinen et al 24 | >10 kg or patient transfers, 5–49x/wk | · | · | 10.00 | 1.2 (0.8 to 1.7) | ||||
| Zhang and Bracken60 | >9 kg, <1x/d | · | · | · | · | · | 12.00 | 0.91 (0.43 to 1.93)¶¶ | |
| (4) Heavy lifting or ≥10 kg—unspecified frequency or ≥1x per day (≥5x/wk) | |||||||||
| Ahlborg et al 19 | ≥12 kg, ≥10x/wk | · | · | · | · | · | 15.00 | 1.16 (0.76 to 1.78) | |
| Axelsson et al 61 | Heavy lifting | · | 7.00 | 1.36 (0.91 to 2.02) | |||||
| Axelsson et al 62 | Heavy lifting | · | 6.75 | 0.99 (0.75 to 1.31) | |||||
| Elliott et al 63 | Heavy lifting | · | 7.50 | 0.69 (0.31 to 1.53) | |||||
| Hansteen et al 59 | Heavy lifting, >1x/d | · | · | 9.00 | 0.90 (0.65 to 1.25)‡‡ | ||||
| Juhl et al
21
(SA<13 wk) | 11–20 kg and >20 kg, 1–10x/d | · | · | · | · | 11.75 | 1.30 (1.06 to 1.60) | ||
| Lerman et al 27 | Heavy lifting, >25x/wk | · | 7.00 | 0.51 (0.30 to 0.85) | |||||
| Maconochie et al 64 | Heavy lifting | · | · | 9.00 | 1.08 (0.85 to 1.38) | ||||
| McDonald et al 65 | Heavy lifting | · | · | · | 9.50 | 1.09 (0.98 to 1.21)‡‡ | |||
| McDonald et al 22 | Heavy lifting,<15x/d | · | · | · | · | 11.00 | 1.28 (1.18 to 1.39)† | ||
| Zhang and Bracken60 | >9 kg, ≥1x/d | · | · | · | · | · | 12.00 | 1.71 (1.25 to 2.32)¶¶ | |
| (5) Heavy lifting or ≥10 kg −≥10x per day (≥50x/wk) or often | |||||||||
| Ahlborg et al 19 | ≥12 kg, >50x/wk | · | · | · | · | · | 15.00 | 1.06 (0.62 to 1.81) | |
| Axelsson et al 20 | ≥10 kg, >50x/wk | · | · | · | 10.00 | 0.74 (0.46 to 1.19) | |||
| Juhl et al
21
(SA<13 wk) | 11–20 kg or >20 kg, >10x/d | · | · | · | · | 11.75 | 1.36 (0.96 to 1.92)*** | ||
| Juhl et al
21
(SA 13–21 wk) | 11–20 kg or >20 kg, >10x/d | · | · | · | · | 11.75 | 1.21 (0.81 to 1.81)*** | ||
| McDonald et al 22 | Heavy lifting, ≥15x/d | · | · | · | · | · | 13.00 | 1.32 (1.17 to 1.48)††† | |
| Taskinen et al 23 | ≥10 kg, continuously | · | 10.25 | 5.7 (1.3 to 26.0) | |||||
| Taskinen et al 24 | >10 kg or patient transfers, ≥50x/wk | · | · | 10.50 | 3.4 (1.3 to 8.7) | ||||
High validity scores (> 12) are in bold.
A dot indicates that the feature is present in the study.
*ORs or relative risks.
†95% CI calculated using Epi Info with data provided in the report.
‡RE obtained by combining the results corresponding to the three following exposure categories: (>6.8 kg, 1–9x/wk), (>6.8 kg, 10–15x/wk) and (>6.8 kg, >15x/wk), assuming non-independence for the 95 % CI.
§Group 1: Fabrication-room working women exposed to any etching fluoride or any photoresist and developer solvents.
¶Group 2: Fabrication-room working women unexposed to any etching fluoride or any photoresist and developer solvents.
**Group 3: Non-fabrication working women.
††RE obtained by combining the results corresponding to the two following exposure categories: (≥10 kg, <10x/ wk) and (≥10 kg, 10–50x/wk), assuming non independence for the 95 % CI.
‡‡RE and 95% CI calculated using Epi Info with data provided in the report.
§§RE obtained by combining the results corresponding to the four following exposure categories: (11–20 kg, 1–3x/d), (11–20 kg, 4–10x/d), (>20 kg, 1–3x/d) and (>20 kg, 4–10x/d), assuming non independence for the 95% CI.
¶¶Unexposed included non-working women but similar result is obtained after exclusion of non-working women.
***RE obtained by combining the results corresponding to the two following exposure categories: (11–20 kg, >10x/d) and (>20 kg, >10x/d), assuming non independence for the 95% CI.
†††CI 95% from the following report: ‘The “Retrait Préventif”: An Evaluation’ by McDonald et al 66. Other RE obtained by period are 1.33 (95% CI 1.11 to 1.58) for SA <10 wk, 1.51 (1.30 to 1.73) for SA 10–15 wk and 1.61 (1.18 to 2.10) for SA 16–27 wk.
d, day; RE, risk estimate; SA, spontaneous abortion; wk, week.