A new Danish study has linked physical activities at work—specifically bending, walking, and standing—to an increased risk of miscarriage during early pregnancy. The research, which tracked over 800,000 pregnancies in Denmark between 2004 and 2018, found that each additional hour of forward bending per day raised the risk of miscarriage by 36%. Walking was associated with an 18% increase per extra hour, while standing showed a 3% increase. However, experts caution that these findings should not cause undue alarm, as most miscarriages result from random genetic abnormalities unrelated to maternal actions.
Study Methodology and Key Findings
The researchers from Denmark used national health and employment records to analyze pregnancies from 2004 to 2018. They matched each woman's job title to a database estimating the physical demands of various occupations, including standing, walking, and bending. The database was built using motion sensors worn by 403 pregnant Danish workers, combined with expert ratings for each job. The study did not directly survey women about their activities at work.
Just over 10% of pregnancies in the study ended in miscarriage. Among the three activities, forward bending showed the strongest association with miscarriage risk, with a 36% increase for each additional hour per day. The effect for standing was minimal—a 3% increase per hour—and nearly disappeared after adjusting for smoking. Walking fell in between, with an 18% increased risk per extra hour. However, these percentages apply to additional hours above baseline levels. For example, the typical worker bent forward for about 24 minutes over an eight-hour shift. If the baseline miscarriage risk is 10 in 100, an extra hour of bending might raise it to about 13 in 100.
Limitations and Confounding Factors
The study has significant blind spots, particularly regarding smoking. Nearly 10% of women in the most physically demanding jobs smoked during pregnancy, compared to about 4% in the least demanding jobs. While researchers attempted to adjust for smoking, they lacked individual smoking data for most participants. Smoking is one of the strongest risk factors for miscarriage. Other unmeasured factors include body weight, thyroid dysfunction, diabetes, mental health, and fertility treatment, all of which affect miscarriage risk.
Forward bending often coincides with heavy lifting, which other research has more clearly tied to miscarriage. The Danish team could not separate these two activities. Additionally, women in the highest-exposure jobs did not have the highest miscarriage risk, suggesting that physical work may not be the primary driver.
What Causes Miscarriage?
Most miscarriages are caused by random genetic mutations in the fetus, which the body recognizes and releases. The risk of such abnormalities increases with maternal age, especially after 35. A large Norwegian study found that about 10% of pregnancies miscarry at age 25, rising to over 50% by age 45. Other risk factors include smoking, heavy drinking, very high or low body weight, uncontrolled diabetes or thyroid disease, infections, previous miscarriages, stress, maternal age under 20, night shifts, air pollution, and pesticide exposure.
Recommendations for Pregnant Women
Despite the findings, experts emphasize that the benefits of staying active during pregnancy are well established. Regular walking and moderate exercise lower the risk of gestational diabetes, excessive weight gain, high blood pressure, and depression. Australian guidelines recommend 150 to 300 minutes of moderate activity per week during pregnancy, unless a doctor advises otherwise. The Danish study specifically examined hours of standing or walking on hard floors at work, which differs from a leisurely 30-minute walk around the block.
If your job involves significant bending—such as in aged care, nursing, cleaning, hairdressing, or shelf stacking—it is reasonable to ask your employer about adjusting duties, even in the first trimester. Suggestions include taking sitting breaks, using a stool for tasks that don't require standing, swapping the heaviest jobs with a colleague, and wearing comfortable footwear.
According to the study's authors, the evidence is not strong enough to support a causal link between physical activity at work and miscarriage risk. The vast majority of miscarriages would have occurred regardless of what a woman did. As one expert noted, "Most miscarriages have nothing to do with what a woman did or didn’t do."
