Ergonomic demands and fetal loss in women in welding and electrical trades: A Canadian cohort study.

Objectives: To determine the relationship between ergonomic demands of the job at conception and fetal loss (miscarriage or stillbirth).

Methods: Women with a welding or electrical trade apprenticeship were identified across Canada for the Women's Health in Apprenticeship Trades-Metal and Electrical study. They completed a reproductive and employment history at recruitment and every 6 months for up to 5 years to provide details on pregnancies and work demands. Job at conception was identified and fetal loss examined in relation to ergonomic exposures/demands, allowing for potential confounders.

Results: A total of 885 women were recruited; 447 in welding and 438 in electrical trades. Of these, 574 reported at least one pregnancy. Analysis of 756 pregnancies since the woman started in her trade suggested no increased risk of fetal loss in those choosing welding rather than electrical work. Among 506 pregnancies conceived during a period working in a trade, 148 (29.2%) ended in fetal loss: 31.2% (73/234) in welding, and 27.6% (75/272) in electrical work. Detailed exposure information was available for 59% (299/506) of these pregnancies. In welders, the risk of fetal loss was increased with whole-body vibration (prevalence ratio [PR] = 2.14; 95% confidence interval [CI] 1.39-3.31) and hand-arm vibration for > 1 hour/day (PR = 2.15; 95% CI 1.33-3.49). In electrical workers risk increased with more than 8 days working without a rest day (PR = 2.29; 95% CI 1.25-4.17). Local exhaust ventilation reduced risk in welders.

Conclusions: There was no significant increase in fetal loss in welding trades compared to electrical work. Vibration, largely from grinding, and extended work rotations appear to be potentially modifiable factors of some importance.