Descriptive summary of the associations between reviewed activities and pregnancy outcomes (1966–2011)*
| Outcome/exposure | All studies | Higher quality larger studies† | ||||||
|---|---|---|---|---|---|---|---|---|
| N Studies | Median (IQR) | Range | N estimates (RR≥2.0/all estimates) | N Studies | Median (IQR) | Range | N estimates (RR≥2.0/all estimates) | |
| Preterm delivery (RR) | ||||||||
| Working hours | 25 | 1.18 (1.00 to 1.34) | 0.30 to 3.69 | 2/30 | 11 | 1.10 (1.01 to 1.21) | 0.30 to 1.60 | 0/15 |
| Shift work | 21 | 1.10 (0.67 to 1.60) | 0.67 to 5.60 | 3/33 | 9 | 1.03 (0.94 to 1.16) | 0.67 to 1.80 | 0/19 |
| Standing | 28 | 1.16 (1.00 to 1.35) | 0.58 to 4.10 | 3/36 | 10 | 1.09 (0.92 to 1.23) | 0.76 to 1.69 | 0/12 |
| Lifting | 17 | 1.12 (0.90 to 1.30) | 0.55 to 2.91 | 1/22 | 11 | 1.02 (0.90 to 1.30) | 0.55 to 1.49 | 0/15 |
| Physical activity | 33 | 1.20 (1.10 to 1.70) | 0.71 to 4.10 | 4/35 | 8 | 1.10 (1.04 to 1.16) | 0.87 to 1.25 | 0/9 |
| SGA (RR) | ||||||||
| Working hours | 14 | 1.10 (1.00 to 1.27) | 0.80 to 2.10 | 1/18 | 6 | 1.10 (1.00 to 1.10) | 0.99 to 1.19 | 0/9 |
| Shift work | 11 | 1.25 (0.94 to 1.49) | 0.70 to 3.31 | 2/18 | 6 | 1.00 (0.92 to 1.25) | 0.70 to 1.50 | 0/11 |
| Standing | 12 | 1.00 (0.93 to 1.26) | 0.86 to 2.00 | 1/17 | 4 | 1.06 (0.98 to 1.24) | 0.89 to 1.42 | 0/4 |
| Lifting | 7 | 1.03 (0.73 to 1.15) | 0.50 to 1.20 | 0/11 | 4 | 1.08 (1.04 to 1.17) | 0.65 to 1.20 | 0/6 |
| Physical activity | 13 | 1.00 (0.82 to 1.38) | 0.70 to 2.40 | 2/14 | 5 | 0.88 (0.81 to 1.00) | 0.76 to 1.20 | 0/6 |
| Low birth weight (RR) | ||||||||
| Working hours | 8 | 1.34 (1.20 to 1.65) | 0.96 to 1.80 | 0/10 | 0 | – | – | - |
| Shift work | 7 | 1.28 (1.02 to 1.47) | 0.71 to 2.10 | 1/9 | 1 | – | 1.02 | 0/1 |
| Standing | 9 | 1.13 (0.70 to 1.58) | 0.50 to 1.92 | 0/13 | 1 | – | 0.5 | 0/1 |
| Lifting | 7 | 1.10 (0.70 to 1.26) | 0.50 to 2.40 | 1/9 | 3 | 0.75 (0.73 to 1.58) | 0.70 to 2.40 | 1/3 |
| Physical activity | 10 | 1.13 (1.04 to 1.80) | 0.60 to 4.32 | 2/11 | 1 | – | 0.99 to 1.13 | 0/2 |
| Birth weight (gms diff) | ||||||||
| Working hours | 7 | −60 (−74 to 7) | −84 to −32 | (N=9) | 3 | −45 (−53 to 44) | −60 to 43 | (N=3) |
| Shift work | 6 | 10 (−273 to 39) | −438 to 195 | (N=13) | 1 | 37 (21 to 57) | 2 to 91 | (N=4) |
| Standing | 8 | −25 (−31 to 0.5) | −49 to 20 | (N=11) | 3 | −36 (−42 to 29) | −49 to 18 | (N=4) |
| Lifting | 3 | −21 (−24 to 11) | −44 to 19 | (N=8) | 0 | – | – | – |
| Physical activity | 8 | −59 (−148 to 29) | −216 to 183 | (N=14) | 2 | – | −21 to 51 | (N=2) |
| Pregnancy-induced hypertension | ||||||||
| Working hours | 5 | 1.10 (0.85 to 1.10) | 0.76 to 1.18 | 0/5 | 1 | – | 0.76 | 0/1 |
| Shift work | 2 | – | 0.90 to 1.10 | 0/2 | 0 | – | – | – |
| Standing | 4 | 1.05 (0.93 to 1.14) | 0.70 to 1.26 | 0/4 | 1 | – | 1.26 | 0/1 |
| Lifting | 2 | – | 1.10 to 1.10 | 0/2 | 0 | – | – | – |
| Physical activity | 4 | 1.15 (1.00 to 1.77) | 0.70 to 3.47 | 1/4 | 0 | – | – | – |
| Pre-eclampsia | ||||||||
| Working hours | 2 | – | 0.96 to 1.20 | 0/2 | 1 | – | 0.96 | 0/1 |
| Shift work | 2 | – | 1.00 to 1.30 | 0/2 | 1 | – | 1.30 | 0/1 |
| Standing | 4 | 0.77 (0.72 to 1.34) | 0.70 to 2.90 | 1/4 | 1 | – | 0.72 | 0/1 |
| Lifting | 3 | 1.1 | 0.68 to 1.70 | 0/3 | 0 | – | – | – |
| Physical activity | 3 | 0.75 | 0.70 to 2.10 | 1/3 | 0 | – | – | – |
*See online supplementary tables S1 to S7 for a complete listing of the reports and associated risk estimates summarised in this table.
†After excluding estimates with higher potential for bias or confounding, involving <1000 deliveries, or from incompletely reported studies.
RR, relative risk; SGA, small for gestational age