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A large Danish study offers new evidence that physically demanding work during early pregnancy may raise the odds of miscarriage, particularly among women whose jobs require frequent forward bending. Researchers examined records for more than 800,000 pregnancies among working women in Denmark between 2004 and 2018, drawing on a national registry that captured occupation codes at the start of each pregnancy. Roughly one in ten of these pregnancies, about 81,000, ended in miscarriage.
Rather than relying on women's memories of how physically taxing their jobs were, the team used a specialized measurement system built for pregnant workers. This tool combined motion-sensor data collected from hundreds of working women across many job types with expert assessments covering over a thousand occupation categories, producing estimates of how many hours per shift a woman likely spent standing, walking, or bending her torso at least 30 degrees forward, based on her job at conception.
The results pointed most clearly to forward bending as a risk factor. Each additional hour of bending per shift corresponded to a 36 percent increase in miscarriage risk after adjusting for factors like age, education, and prior pregnancies. Walking showed an 18 percent increase per hour, and standing showed a smaller but still statistically notable 3 percent rise per hour. Bending was also unique in showing a steady, escalating relationship between exposure and risk, whereas the associations with standing and walking leveled off or grew less certain at the highest exposure levels.
A notable part of the analysis compared women who had taken sick leave in the week before their miscarriage with those who had continued working right up until the loss. Both groups showed elevated risk, which the researchers say weakens the argument that the pattern simply reflects women who were already unwell, and instead lends some support to a genuine causal connection between these physical job demands and pregnancy loss.
Untangling this from smoking proved difficult. Women in the most physically strenuous jobs tended to be younger, less educated, and more likely to smoke during pregnancy, but actual smoking records are typically gathered around the twentieth week, well after most miscarriages occur. To compensate, researchers used a statistical estimate of each woman's likelihood of smoking based on her age and the calendar year. Once they factored this in, the association with standing weakened substantially, while the links to walking and bending remained strong. The team acknowledged this workaround is imperfect and called for future research that tracks individual smoking habits directly.
The authors note several limitations: other hazards common in demanding jobs, such as night shifts or chemical exposure, could be contributing to what they observed, since these conditions often overlap. Job codes were only updated annually, so women who switched to lighter duties partway through pregnancy wouldn't have that change reflected in the data, and the study couldn't separate the effects of bending from lifting, which frequently happen together.
Denmark currently has no formal workplace guidelines addressing standing, walking, or bending during the first four months of pregnancy. While stopping short of calling for immediate policy change, the researchers argue that if the pattern holds up in future studies, early pregnancy deserves a more defined place in workplace safety guidance, given how many women, from nurses to retail workers to teachers, spend their shifts on their feet.