Denmark: A large Danish study has found that frequent forward bending and prolonged walking at work during the early stages of pregnancy may be linked to a higher risk of miscarriage, although researchers stress that the findings do not prove these activities directly cause pregnancy loss.
The research, published in the journal Occupational and Environmental Medicine, analysed 803,829 pregnancies among 475,312 women in Denmark between 2004 and 2018. Of these, 81,307 pregnancies ended in miscarriage.
Using a pregnancy-specific job exposure model that combined activity tracker data with expert assessments, researchers from Bispebjerg Hospital and the University of Copenhagen evaluated workplace activities such as standing, walking and forward bending at angles of 30 degrees or more.
The study found that each additional hour of forward bending during an eight-hour workday was associated with a 36 percent increase in the risk of miscarriage. Every extra hour spent walking was linked to an 18 percent higher risk, while each additional hour of standing was associated with a 3 percent increase.
Miscarriage affects around 15 percent of pregnancies, with established risk factors including parental age, smoking, night shift work, air pollution and exposure to certain chemicals. Previous studies examining the impact of workplace physical activity have produced mixed results.
Researchers believe occupational activities such as prolonged forward bending may affect placental blood flow or hormonal regulation, potentially increasing miscarriage risk. However, they emphasised that the study was observational and could not establish a direct cause-and-effect relationship.
The researchers also acknowledged several limitations, including the absence of individual data on smoking during pregnancy and the inability to account for other factors such as heavy lifting, shift work and chemical exposure.
They called for further research to confirm the findings and suggested that early pregnancy should receive greater attention when developing workplace guidelines for pregnant employees. Commenting on the study, Prof. Asma Khalil, Professor of Obstetrics and Maternal Medicine at City St George’s, University of London, who was not involved in the research, said the results should not be interpreted as evidence that normal movement during pregnancy is unsafe.
Khalil described the research as a large, well-designed nationwide study that reduced recall bias by using objective exposure estimates rather than self-reported data. However, Khalil noted that the observational nature of the study means it cannot prove causation and highlighted important limitations, including the lack of information on smoking, lifting and other workplace exposures.
Khalil said the findings present an important hypothesis but require confirmation in other populations before they can be used to shape specific workplace recommendations for pregnant women.
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