Table 5 Occupational activity and the risks of pre‐eclampsia and pregnancy‐induced hypertension.
| First author (year) | Outcome | Numbers in analysis | RR (95% CI) | Exposure | Higher potential for | Incomplete reporting | ||
|---|---|---|---|---|---|---|---|---|
| Comparison | Timing | Bias | Confounding | |||||
| Weekly working hours | ||||||||
| Cohort studies | ||||||||
| Landsbergis PA (1996)22 | PIH | 575 | 1.1 (0.2 to 5.7) | 41–49 vs <35 h/wk | Trimester 1 | No | No | No |
| Case–control studies | ||||||||
| Marcoux S (1999)28 | PIH | 267 | 0.85 (0.48 to 1.54) | ⩾35 vs ⩽21 h/wk | First 20 weeks | No | No | No |
| Shift work | ||||||||
| Cross‐sectional studies | ||||||||
| Nurminen T (1989)34 | PIH | 890 | 0.9 (0.4 to 1.9) | 2 or 3 shift work vs none | Most of pregnancy | No | Yes | No |
| Wergeland E (1997)53 | PE | 3281 | 1.3 (0.8 to 1.9) | Shift work (yes vs no) | Trimester 1 | No | No | No |
| Lifting | ||||||||
| Cross‐sectional studies | ||||||||
| Irwin DE (1994)19 | PIH | 2413 | 1.1 (0.8 to 1.6) | ⩾13.6 vs ⩽4.5 kg/d | Not stated | No | Yes | No |
| Irwin DE (1994)19 | PE | 2420 | 0.68 (0.47 to 0.98) | ⩾13.6 vs ⩽4.5 kg/d | Not stated | No | Yes | No |
| Wergeland E (1997)53 | PE | 3284 | 1.7 (1.2 to 2.5) | Lifting heavy loads (10–20 kg; yes vs no) | Trimester 1 | Yes | No | No |
| Standing | ||||||||
| Cohort studies | ||||||||
| Saftlas AF (2004)41 | PIH | 1009 | 1.26 (0.83 to 1.91) | Sitting <34% vs ⩾67% of the time | Trimester 1 | No | No | No |
| Saftlas AF (2004)41 | PE | 1009 | 0.72 (0.32 to 1.59) | Sitting <34% vs ⩾67% of the time | Trimester 1 | No | No | No |
| Cross‐sectional studies | ||||||||
| Irwin DE (1994)19 | PIH | 2882 | 1.0 (0.71 to 1.4) | ⩾2/3 vs ⩽1/3 of time | Not stated | No | Yes | No |
| Nurminen T (1989)35 | PIH | 687 | 1.1 (0.6 to 2.0) | Standing work vs sedentary | Trimester 3 | Yes | Yes | No |
| Irwin DE (1994)19 | PE | 2879 | 0.82 (0.57 to 1.2) | ⩾2/3 vs ⩽1/3 of time | Not stated | No | Yes | No |
| Wergeland E (1997)53 | PE | 3294 | 0.7 (0.5 to 1.0) | Standing/walking (yes vs no) | Trimester 1 | Yes | No | No |
| Physical activity | ||||||||
| Cohort studies | ||||||||
| Landsbergis PA (1996)22 | PIH | 575 | 0.7 (0.2 to 2.5) | Physical activity score (>200 vs ⩽200) | Trimester 1 | No | No | No |
| Landsbergis PA (1996)22 | PE | 575 | 0.7 (0.2 to 2.5) | Physical activity score (>200 vs ⩽200) | Trimester 1 | No | No | No |
| Case–control studies | ||||||||
| Spinillo A (1995)48 | PE | 480 | 2.1 (1.18 to 3.75) | Activity score (moderate/high vs mild/none) | Trimester 1 | Yes | No | No |
| Cross‐sectional studies | ||||||||
| Irwin DE (1994)19 | PIH | 2665 | 1.2 (0.83 to 1.6) | ⩾2/3 vs ⩽1/3 of time | Not stated | No | Yes | No |
| Irwin DE (1994)19 | PE | 2668 | 0.75 (0.52 to 1.1) | ⩾2/3 vs ⩽1/3 of time | Not stated | No | Yes | No |
| Nurminen T (1989)35 | PIH | 529 | 1.1 (0.4 to 3.2) | Work with a moderate physical load vs sedentary | Trimester 3 | Yes | Yes | No |
| Saurel‐Cubizolles MJ (1985)42 | PIH | 591 | 3.47 (2.04 to 5.83) | Activity score (2/3 vs 0/1 strenuous items) | Not stated | Yes | Yes | Yes |
h/wk, hours per week; kg/d, kilograms per day; PE, pre‐eclampsia.
RR is used generically to encompass a variety of published effect measures (odds ratios, incidence density ratios, hazard ratios etc).