Table 3 Lifting, physical activity and risk of preterm delivery.
| First author (year) | Numbers in analysis | RR (95% CI) | Exposure | Higher potential for | Incomplete reporting | ||
|---|---|---|---|---|---|---|---|
| Comparison | Timing | Bias | Confounding | ||||
| Lifting | |||||||
| Cohort studies | |||||||
| Ahlborg GJ (1990)5 | 3389 | 1.29 (0.69 to 2.4) | ⩾12 kg >50 x/wk vs none | Not stated | No | No | No |
| Brink‐Henriksen T (1995)10 | 3410 | 0.93 (0.45 to 1.75) | Lifting ⩾12 kg ⩾10 x/d vs never | 16 weeks | No | No | No |
| Magann EF (2005)26 | 318 | 1.14 (0.32 to 3.18) | Lifting ⩾11 kg >6 x/h | Trimester 1 | No | No | No |
| Misra DP (1998)32 | 1166 | 1.49 (0.61 to 3.28) | Lifting heavy objects on the job (yes vs no) | Trimesters 1 and 2 | No | No | No |
| Pompeii LA (2005)38 | 1176 | 1.3 (0.9 to 1.8) | Lifting ⩾25 lbs ⩾13 vs 0 x/wk | Trimester 1 | No | No | No |
| Pompeii LA (2005)38 | 1176 | 1.3 (0.8 to 2.1) | Lifting ⩾25 lbs ⩾13 vs 0 x/wk | Trimester 2 | No | No | No |
| Pompeii LA (2005)38 | 1176 | 1.3 (0.6 to 2.9) | Lifting ⩾25 lbs ⩾13 vs 0 x/wk | Trimester 3 | No | No | No |
| Tuntiseranee P (1998)52 | 1108 | 0.9 (0.4 to 2.1) | >12 kg, 1–10 x/d vs none | 15–28 weeks | No | No | No |
| Case–control studies | |||||||
| Berkowitz GS (1983)7 | 231 | 0.81 (0.43 to 1.49) | Lifting on the job | Not stated | No | Yes | No |
| Saurel‐Cubizolles MJ (2004)45 | 4786 | 1.02 (0.8 to 1.2) | Loads carried >20 kg vs none | Trimester 1 | No | No | No |
| Cross‐sectional studies | |||||||
| Fortier I (1995)13 | 3078 | 0.87 (0.52 to 1.45) | ⩾10 kg vs none | Not stated | No | No | No |
| McDonald AD (1988)29 | 22761 | 1.25, p<0.01 | Lifting heavy weights ⩾15 vs <15 x/d | Not stated | No | No | No |
| Saurel‐Cubizolles MJ (1987)43 | 2262 | 1.35 (0.77 to 2.24) | Carrying of heavy loads (yes vs no) | Trimester 1 | No | Yes | No |
| Saurel‐Cubizolles MJ (1991)44 | 874 | 1.31 (0.64 to 2.58) | Lifting heavy loads (often/always vs none/sometimes | Not stated | No | No | No |
| Physical activity | |||||||
| Cohort studies | |||||||
| Hickey CA (1995)17 | 612 | 0.7 (0.41 to 1.18) | Occupational fatigue score (⩾3 vs <3) | 24–26 weeks | No | No | No |
| Klebanoff MA (1990)21 | 7100 | 1.04 (0.76 to 1.42) | Heavy work ⩾4 vs 0 h/d | 1–5 months | No | No | No |
| Launer LJ (1990)23 | 4168 | 1.11 (0.77 to 1.62) | Manual vs office work | Not stated | No | No | No |
| Magann EF (1996)25 | 531 | 1.26 (0.64 to 2.6) | >2900 vs <2300 kcal/d energy expenditure | 16–18 weeks | No | Yes | No |
| Newman RB (2001)33 | 1218 | 1.17 (1.01 to 1.35) | Physical activity score | 22–24 weeks | No | No | No |
| Rao S (2003)40 | 508 | 0.8 (0.4 to 1.6) | High vs low activity | 18 weeks | No | No | No |
| Rao S (2003)40 | 485 | 1.2 (0.6 to 2.3) | High vs low activity | 28 weeks | No | No | No |
| Stinson JC (2003)49 | 359 | 1.79 (0.93 to 3.44) | Fatigue score >660 (severe vs ⩽660) high vs low | 22–26 weeks | No | No | No |
| Tuntiseranee P (1998)52 | 346 | 1.2 (0.4 to 3.8) | High vs low | 15–28 weeks | No | No | No |
| Case–control studies | |||||||
| Hartikainen‐Sorri AL (1989)15 | 358 | 0.81 (0.46 to 1.43) | Heavy physical loading (yes vs no) | Not stated | No | Yes | No |
| Luke B* (1995)24 | 1470 | 1.4 (1.1 to 1.9) | Occupational fatigue score (⩾3 vs <3) | Not stated | Yes | No | Yes |
| Cross‐sectional studies | |||||||
| Ceron‐Mireles P (1996)11 | 2429 | 1.25 (0.97 to 1.6) | Job requires physical effort (yes vs no) | Not stated | No | No | No |
| Fortier I (1995)13 | 1829 | 0.87 (0.49 to 1.54) | Important vs none | Not stated | No | No | No |
| Homer CJ (1990)18 | 773 | 2.0 (1.1 to 3.9) | High vs low exertion job | Not stated | No | No | No |
| Mamelle N (1984)27 | 1928 | 1.7 (1.1 to 2.0) | High vs low exertion | Not stated | No | Yes | No |
| McDonald AD (1988)29 | 22761 | 1.1, p>0.05 | Great physical effort (yes vs no) | Not stated | No | No | No |
| Nurminen T (1989)35 | 675 | 1.4 (1.1 to 1.7) | Work with a moderate physical load vs sedentary | Trimester 3 | No | No | No |
| Peoples‐Sheps MD (1991)36 | 535 | 1.1 (0.6 to 2.1) | High vs low strength requirement | Not stated | No | No | No |
| Ramirez G* (1990)39 | 1960 | 1.75 (1.12 to 2.75) | Very heavy vs low physical demands | Not stated | No | No | Yes |
| Saurel‐Cubizolles MJ (1985)42 | 580 | 4.11 (2.15 to 7.78) | Activity score (2/3 vs 0/1 strenuous items) | Not stated | No | Yes | No |
| Saurel‐Cubizolles MJ (1987)43 | 2262 | 2.13 (1.16 to 3.76) | Activity score (3/4 items vs none) | Trimester 1 | No | Yes | No |
| Saurel‐Cubizolles MJ (1991)44 | 874 | 1.2 (0.5 to 2.5) | Activity score (2/3 vs 0/1 items) | Not stated | No | No | No |
x/day, times per day; x/wk, times per week.
RR is used generically to encompass a variety of published effect measures (odds ratios, incidence density ratios, hazard ratios, etc).
*Effective response rate <50%.