Women often ask whether they should change what they do at work once they are pregnant. Is it OK to lift, carry on with shift work or work nights? On 12th December a Scandanavian journal published an interesting study on the impact of workload, lifting, standing, working hours and shift work on the likelihood of miscarriage – using meta-analysis and on the basis of a systematic review http://www.ncbi.nlm.nih.gov/pubmed/23235838. Effectively pooling the data of 30 previous studies they found that working fixed nights was associated with a moderately increased risk of miscarriage (pooled relative risk 1.51 [95% confidence interval (95% CI) 1.27-1.78, N=5). Working in 3-shift schedules, working 40 to 52 hours per week, lifting more than 100 kg/day, standing for between 6 and 8 hours/day and physical workload were associated with only very small possible increases in the risk with a pooled relative risk of just 1.12, interesting in this review the impact of hours and standing became less evident the better the quality of the studies.
The conclusion was that the findings were reassuring and did not provide a strong arguement to advise restrictions in the working practices of women in the first trimester of pregnancy. On the other hand it does prove that in individual pregnancies exposure to long hours, standing cannot have an impact. On balence my interpetation is that in general terms women should not feel they have to restrict their working patterns – but in higher risk cases it may be prudent to do so – which mirrors the views expressed by the authors of the paper.