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This systematic review was conducted to help clarify the effect of lifting at work on pregnancy outcome, by focusing on specific exposure categories. A search in Medline and Embase identified 51 articles reporting association of spontaneous abortion (SA), preterm delivery (PTD) or small-for-gestational-age (SGA) infant with exposure to occupational lifting. A global validity score was assigned to each study and six potential sources of bias were considered in sensitivity analyses. For each exposure–outcome combination, a summary risk estimate (RE) was obtained from all studies and from a subset of studies with high validity score, this latter summary RE was selected as a final result. Statistical heterogeneity was measured with I2 and Q tests and the possibility of a publication bias was also assessed. For each meta-analysis, the strength of evidence was established from explicit criteria. Heavy (or ≥10 kg) loads often (or ≥10x/day) lifted were associated with increased risks of SA (summary RE=1.31, 95% CI 1.17 to 1.47) and PTD (summary RE=1.24, 95% CI 1.07 to 1.43), with good strength of evidence. No association was identified with SGA, nor with lower exposure levels and SA or PTD. These results are reassuring for lower levels of exposure; however, observed associations can guide health professionals’ recommendations aimed at the prevention of SA and PTD for pregnant women who frequently lift (or ≥10x/day) heavy (or ≥10 kg) loads at work.Résumé

Objectives. We undertook a case–control study to evaluate whether some occupational conditions during pregnancy increase the risk of delivering a small-for-gestational-age (SGA) infant and whether taking measures to eliminate these conditions decreases that risk. Methods. The 1536 cases and 4441 controls were selected from 43898 women who had single live births between January 1997 and March 1999 in Québec, Canada. The women were interviewed by telephone after delivery. Results. The risk of having an SGA infant increased with an irregular or shift-work schedule alone and with a cumulative index of the following occupational conditions: night hours, irregular or shift-work schedule, standing, lifting loads, noise, and high psychological demand combined with low social support. When the conditions were not eliminated, the risk increased with the number of conditions (Ptrend =.004; odds ratios=1.00, 1.08, 1.28, 1.43, and 2.29 for 0, 1, 2, 3, and 4–6 conditions, respectively). Elimination of the conditions before 24 weeks of pregnancy brought the risks close to those of unexposed women. Conclusions. Certain occupational conditions experienced by pregnant women can increase their risk of having an SGA infant, but preventive measures can reduce the risk.

Objectives Preeclampsia is a leading cause of maternal and perinatal morbidity. Work-related factors may influence the occurrence of this disorder. This case–control study estimated the associations between work-related physical and psychosocial factors and the risk of preeclampsia and gestational hypertension. Methods The eligible women consisted of a random sample of the women who delivered a singleton live birth in 1997–1999 in six regions of Quebec and worked during pregnancy. Cases of preeclampsia (N=102) and gestational hypertension (N=99) were compared with normotensive controls (N=4381). Information on occupational exposures at the onset of pregnancy was collected during phone interviews a few weeks after delivery. Detailed information was obtained on work schedule, postures, physical exertion, work organization, noise, vibration, and extreme temperature. Adjusted odds ratios (aOR) were estimated through polytomous logistic regression. Results Women standing daily at least 1 hour consecutively without walking experienced a higher risk of preeclampsia [aOR 2.5, 95% confidence interval (95% CI) 1.4–4.6], as well as women climbing stairs frequently (aOR 2.3, 95% CI 1.2–4.1) and women working more than 5 consecutive days without a day-off (aOR 3.0, 95% CI 1.0–9.5). Squatting or kneeling, pushing or pulling objects, whole-body vibration, forced pace, job strain, and no control on breaks were positively, but nonsignificantly, associated with preeclampsia. The associations were weaker for gestational hypertension. Conclusions These findings suggest that being exposed to physically demanding and stressful occupational conditions at the onset of pregnancy increases the risk of preeclampsia.

The objective of this case-control study was to evaluate whether occupational conditions during pregnancy are associated with preterm delivery (PTD). Women whose work conditions changed following the use of a legally justified preventive measure (withdrawal from work or job reassignment) were also compared with those whose work conditions did not change. Cases (n = 1,242) and controls (n = 4,513) were selected from 43,898 women who had single livebirths between January 1997 and March 1999 in Quebec, Canada. They were interviewed by telephone after delivery. Results showed association of PTD with demanding posture for at least 3 hours per day, whole-body vibrations, high job strain combined with low or moderate social support, and a cumulative index composed of nine occupational conditions. The adjusted odds ratio increased from 1.0 to 2.0 for PTD (ptrend < 0.0001) and from 1.0 to 2.7 for very PTD (