Standing, walking, and bending may increase the risk of miscarriage, researchers said in a new paper.
Pregnant women who had to move as part of their job were more likely to suffer miscarriage, or the unwanted sudden loss of pregnancy, according to researchers in Denmark.
For each hour of occupational standing, walking, and bending forward at least 30 degrees, there was an elevated risk of miscarriage, Hannah Nortoft Frankel, a medical doctor at the Bispebjerg Hospital’s Department of Occupational and Environmental Medicine, and co-authors said.
For each additional hour of occupational bending forward, the risk of miscarriage was increased 36 percent. For each additional hour of walking on the job, the risk was increased by 18 percent. For each additional hour of standing during employment, the risk was 3 percent higher.
“Although the mechanisms are not completely understood, these occupational exposures may affect placental perfusion or hormonal regulation in ways that could increase the risk of miscarriage,” the authors stated.
The study was published by BMJ Journals on June 18.
A small number of studies previously identified a potential risk of miscarriage for women who move as part of the occupations, including for women who lift during the workday. A previous meta-analysis found an increased risk of miscarriage for bending forward, but a systematic review did not identify a link between occupational standing and miscarriage.
The researchers behind the new paper wanted to fill what they described as a data gap and examined information from multiple databases in Denmark, including the Danish Medical Birth Registry.
They ended up with data on 803,829 pregnancies among 475,312 women. Ten percent of the women suffered miscarriages.
The researchers estimated the risk of miscarriage for standing, walking, and bending forward independently, with the definition of miscarriage as the loss of pregnancy before the 22nd week of gestation.
Kevin McConway, emeritus professor of applied statistics at Open University, who was not involved with the research, said in a statement that the study was observational and could not prove the movements actually increase risk of miscarriage.
“We can’t conclude that bending over at work, or walking at work, are the cause of an increased miscarriage risk. They could be the cause, or part of the cause, but they might not be,” said McConway.
Listed limitations of the new paper included not being able to capture any job changes during pregnancy, as the employment database only records one annual job.
The researchers said that they attempted to adjust for possible influencing factors, including smoking, but that future research should look at replicating the results in similar populations.
The authors declared no conflicts of interest. Funding for the study came from Working Environment Research Fund and A.P. Moller Foundation grants.