Frequent bending at work may raise miscarriage risk —Study

Frequent bending and prolonged walking at work during early pregnancy may increase the risk of miscarriage, according to new research.

Miscarriage affects about one in seven pregnancies, with established risk factors including advanced parental age, smoking, night-shift work, air pollution, and exposure to certain chemicals. However, the role of workplace physical activities has remained unclear.

A study published in the journal Occupational and Environmental Medicine suggested that certain workplace movements, particularly frequent forward bending, may also contribute to the risk.

Researchers from Bispebjerg Hospital and the University of Copenhagen analysed data from 803,829 pregnancies involving 475,312 Danish women between 2004 and 2018.

Using a pregnancy-specific job exposure model that combined activity tracker data with expert assessments, they estimated the amount of time pregnant women spent standing, walking, and bending forward by at least 30 degrees while at work.

The researchers found that every additional hour spent bending forward during an eight-hour workday was associated with a 36 per cent higher risk of miscarriage. Each extra hour of walking was linked to an 18 per cent increase in risk, while an additional hour of standing was associated with a modest three percent increase.

Overall, about 81,300 pregnancies — roughly one in 10 — ended in miscarriage, slightly lower than the commonly reported prevalence of about 15 per cent. Although the findings point to a possible association between workplace physical activity and miscarriage, the researchers cautioned that the study was observational and could not establish a cause-and-effect relationship.

They also acknowledged several limitations, including the lack of individual data on smoking during pregnancy and other potentially important workplace exposures.

They called for further research to confirm the findings and better understand the biological mechanisms involved, suggesting that repeated forward bending and other physically demanding workplace activities may affect placental blood flow or hormonal regulation during early pregnancy.

The team added that if future studies support the findings, workplace guidelines for pregnant employees may need to place greater emphasis on protecting women during the earliest stages of pregnancy.

Commenting on the findings, a consultant obstetrician and gynaecologist at University College Hospital, Dr Taiwo Tsele, who was not involved in the study, cautioned against interpreting the findings to mean that bending or walking generally causes miscarriage. She said posture alone is not recognised as a direct cause of pregnancy loss.

“In fact, we encourage exercise and walking during pregnancy because they are beneficial to the mother. Posture is not one of the recognised causes of miscarriage,” she said.

Tesla explained that although every pregnancy is different, it would be inaccurate to conclude that routine activities such as bending or walking long distances are responsible for miscarriage.

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“Some people can engage in vigorous activities throughout pregnancy without any problem, while another person may develop complications after minimal exertion. That is why we cannot simply say posture causes miscarriage,” she added.

She noted that the womb is naturally designed to protect the developing pregnancy, making it unlikely that ordinary movements alone would result in pregnancy loss.

According to her, miscarriages are more commonly linked to underlying medical conditions, including cervical incompetence, in which the cervix is unable to remain tightly closed during pregnancy.

“The cervix acts like the opening of a sack. If it is weak and cannot stay closed, the pregnancy may be lost. This is not something a woman can know beforehand until she experiences a miscarriage and is properly evaluated,” she explained.

Tesla said women diagnosed with cervical incompetence can often carry future pregnancies successfully after undergoing cervical cerclage, a procedure in which a stitch is placed around the cervix to keep it closed until the pregnancy reaches term.

“When we identify cervical incompetence, we place a stitch to support the pregnancy. The stitch remains throughout the pregnancy and is removed when it is time for delivery,” she said.

She, however, acknowledged that obstetricians may advise some women with a history of miscarriage to temporarily avoid certain physically demanding activities based on their individual medical history.

“For instance, if a woman who previously had a miscarriage operates a manual sewing machine that requires continuous leg pedalling, we may advise her to stop that activity during pregnancy until we are sure it poses no risk. That advice is based on her medical history, not because posture itself causes miscarriage,” she said.

Tesla added that pregnancy loss may also result from the use of certain medications during pregnancy or underlying medical conditions such as antiphospholipid syndrome, which increases the risk of recurrent miscarriage.

“When a miscarriage occurs, we don’t simply assume what caused it. We investigate to determine the reason and, where necessary, institute treatment to improve the chances of a successful pregnancy next time,” she said.

In addition to antiphospholipid syndrome, more medical conditions that can cause miscarriage include poorly controlled diabetes, abnormalities of the womb, and certain infections. Even advanced mother’s age can increase the risk for a miscarriage.

She urged pregnant women to attend regular antenatal clinics and seek medical advice before making changes to their daily activities, stressing that recommendations should be tailored to each woman’s health status rather than based on general assumptions about posture or movement.

Also commenting on the study, Asma Khalil, professor of obstetrics and maternal medicine and consultant obstetrician at City St George’s, University of London, who was not involved in the research, urged caution in interpreting the findings.

She described the research as a large, well-designed nationwide cohort study, noting that the use of a pregnancy-specific job exposure model reduced recall bias commonly associated with self-reported workplace activities.

According to Khalil, the strongest association observed was between forward bending and miscarriage, with a clearer dose-response relationship than was seen for standing or walking. However, she stressed that the study could not prove that bending or walking directly causes miscarriage.

She also highlighted important limitations, including the inability to account for smoking, heavy lifting, and other workplace factors such as shift work or exposure to hazardous substances.

Khalil said the findings should not be interpreted as evidence that normal movement or routine physical activity during pregnancy is unsafe. Instead, she called for further studies in diverse populations before the results are used to shape workplace recommendations for pregnant women.