Standing at work and preterm delivery

Abstract

Objective Guidelines in some European countries and the United States suggest that pregnant women should avoid prolonged standing and heavy lifting in the workplace during the second and third trimester of pregnancy. However, results from epidemiological studies on this topic are ambiguous. The aim of this study was to evaluate the influence of standing and walking at work in the second trimester on preterm delivery in a population with a low frequency of other workplace hazards. Subjects and design A prospective cohort of 8711 women with singleton pregnancies was established during 1989 through 1991. Information was collected during the 16th week of pregnancy about medical and obstetrical history, general lifestyle factors and exposures at work. The analyses were restricted to 4259 respondents who worked at the 16th week. Potential confounders and effect modifiers were evaluated by stratification and multivariate analyses. Results After adjustment for confounders, women standing more than five hours per work day had an odds ratio (OR) for preterm delivery of 1.2 (95% CI 0.6 to 2.4) compared with women standing two hours or less. For walking, the OR was 1.4 (95% CI 0.7 to 2.5). Many women were unable to separate periods of standing from periods of walking; a combined measure of these two exposures was created to reflect exposure intensity. Women who reported more than five hours of both standing and walking had an adjusted OR of 3.3 (95% CI 1.4 to 8.0) compared with women who reported two hours or less on either of the exposures. No adverse effects were seen for lifting or other types of physical exertion. Conclusions Our findings suggest that standing and walking at work during the second trimester may present a particular risk for preterm delivery, and workplace guidelines are justified. Further research is needed to address the specific mechanisms by which physical exertion, including standing and walking, might cause preterm delivery.

Physical load and psychological demand at work during pregnancy and preterm birth

“…As did McDonald (McDonald et al 1988), we found heavy load carrying to be associated with preterm birth, whereas other authors (Ahlborg et al 1990;Fortier et al 1995;Henriksen et al 1995;Saurel-Cubizolles and Kaminski 1991) found no such association. However, it is dicult to compare the results of dierent studies evaluating the eect of heavy load carrying on preterm birth, due to the variability of the exposure indicator used.…”

“…As found by other authors (Cero n-Mireles et al 1996;Henriksen et al 1995;Savitz et al 1996), the number of weekly working hours did not aect the risk of preterm birth. However, other studies indicate that long hours of work per week increase the risk of preterm birth (Luke et al 1995;McDonald et al 1988).…”

“…In our study we used four variables to characterise the physical workload: standing, strenuous postures, heavy load carrying (more than 5 kg) and an indicator of physical workload calculated from the sum of these three variables. With regard to standing position, some authors found a positive association with preterm birth (Launer et al 1990;Teitelman et al 1990), while other studies failed to report any such association (Cero n- Mireles et al 1996;Fortier et al 1995;Henriksen et al 1995;Saurel-Cubizolles and Kaminski 1991). According to our data, women who stand for more than 6 h a day at work have a greater risk of preterm birth, but the association is on the borderline of statistical signi®cance.…”

Occupational Factors and Risk of Preterm Birth in Nurses

“…15,[19][20][21][22][23][24][25][26][27][28][29][30] . While it has been suggested that heavy lifting may provoke uterine contractions by increasing intra-abdominal pressure, 31 the evidence from our and previous studies does not support an associated increase in risk of preterm births, when adjusting for other occupational risk factors.…”

“…Long working hours are related to increased stress and fatigue due to less time to recover from work. 36,37 Though the categorical definitions of hours worked per week varied, previous studies showed modest, if any, increases in risk, and most failed to show a dose-response relationship, [19][20][21][26][27][28][29]33 except one study of U.S. nurses. 15 Reported exposure to sterilizing agents was associated with a 90% increase in risk of preterm birth in our study, though based on few exposed women.…”