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Key takeawaysAuthor

Key takeaways

  • A Danish study examined more than 800,000 pregnancies and compared estimated levels of bending, walking and standing at work with miscarriage rates.
  • Forward bending showed the strongest association, with the study reporting a 36% relative increase in miscarriage risk for each additional hour per working day.
  • The findings do not establish cause and effect, and the researchers could not fully account for several important factors that influence miscarriage risk.
  • Walking at work is different from moderate exercise, such as taking a 30-minute walk around the neighbourhood.
  • Staying active during pregnancy remains recommended for most people unless a doctor or healthcare professional advises otherwise.
  • Most miscarriages are not preventable and are commonly associated with chromosomal or genetic differences in the developing embryo.

Can bending and walking really increase the risk of miscarriage?

A new Danish study has examined whether physical activity at work during early pregnancy is associated with miscarriage risk. In an article published by The Conversation, Genea Melbourne City Medical Director A/Prof Alex Polyakov explains what the research found, its important limitations, and what the findings mean for people who are pregnant or planning a pregnancy.

While the study found an association between some workplace activities and miscarriage, it does not prove that bending, walking or standing causes miscarriage. Most miscarriages are not caused by something a woman did or did not do.

What did the Danish study investigate?

Researchers used Danish national health and employment records to examine more than 800,000 pregnancies occurring between 2004 and 2018.

Rather than directly measuring each pregnant worker’s activity, the researchers matched women’s job titles with a database estimating how much standing, walking and forward bending would typically be involved in that occupation.

The occupational database had been developed using motion sensors worn by 403 pregnant workers, together with expert assessments of the physical demands associated with different jobs.

Researchers then compared estimated activity levels with miscarriage rates to determine whether greater occupational exposure to standing, walking or bending was associated with a change in risk.

What did the study find?

Just over one in ten pregnancies included in the study resulted in miscarriage.

Of the three activities assessed, forward bending showed the clearest association. The researchers reported a 36% relative increase in miscarriage risk for every additional hour of forward bending during the working day.

Walking was associated with an 18% relative increase for each additional hour, while standing was associated with a smaller increase of approximately 3% per hour. The association with standing was substantially reduced after researchers attempted to account for differences in smoking.

These percentages describe relative changes in risk. They do not mean that walking at work automatically raises every pregnant person’s overall miscarriage risk by 18%.

For example, the typical worker in the study spent approximately 24 minutes bending forward during an eight-hour shift. The article explains that if someone’s baseline miscarriage risk were around ten in 100, an additional hour of bending each day might increase that estimated risk to approximately 13 in 100.

Does the study prove physical work causes miscarriage?

No. The study identified associations, but it could not establish that bending, walking or standing directly caused miscarriages.

One important limitation involved smoking. Almost 10% of women in the most physically demanding jobs smoked during pregnancy, compared with approximately 4% of those in the least physically demanding roles.

Although the researchers tried to adjust for smoking, complete individual smoking information was unavailable for most women. This matters because smoking is an established risk factor for miscarriage.

The data also did not include several other factors that can affect miscarriage risk, including:

  • Body weight
  • Diabetes
  • Thyroid conditions
  • Mental health
  • Fertility treatment
  • Other aspects of individual health and pregnancy history

Forward bending may also occur alongside heavy lifting. Previous research has linked heavy occupational lifting more clearly with miscarriage, but the Danish researchers could not separate the potential effects of lifting from bending.

The results did not show a straightforward pattern across every exposure level, either. Women working in jobs with the greatest estimated physical exposure did not record the highest miscarriage risk. If physical workload were the primary cause, researchers may have expected risk to rise consistently as exposure increased.

What commonly causes miscarriage?

Most miscarriages are not caused by everyday movement, exercise or something a pregnant person has done.

A common cause is a random chromosomal or genetic difference affecting the developing embryo. This can prevent the pregnancy from developing normally and is generally outside anyone’s control.

Age is also an important factor. The likelihood of chromosomal differences and miscarriage increases as a woman gets older, particularly after the age of 35.

Other factors that may influence risk include smoking, heavy alcohol consumption, very high or low body weight, uncontrolled diabetes, thyroid conditions and some infections. Previous miscarriages may also increase someone’s individual risk.

Even when a risk factor is present, it may not be possible to determine exactly why an individual miscarriage occurred.

Should you stop walking during pregnancy?

The study does not provide a reason for most pregnant people to stop walking or exercising.

It examined prolonged standing and walking associated with work, often over hard surfaces and for extended periods. This is different from taking a short walk, swimming or participating in another form of moderate recreational exercise.

Australian physical activity guidelines recommend that pregnant people without medical contraindications aim for 150 to 300 minutes of moderate-intensity activity each week.

Regular activity during pregnancy has established health benefits. It can help reduce the risk of gestational diabetes, excessive weight gain, high blood pressure and depression.

Exercise recommendations may need to be adjusted depending on an individual’s health, pregnancy and medical history. A GP, obstetrician or other healthcare professional can provide personalised advice.

What if your job involves frequent bending or standing?

People working in nursing, aged care, cleaning, hairdressing, retail, warehousing or similar roles may spend long periods standing or repeatedly bending during a shift.

The study does not prove these activities cause miscarriage, but it may still be reasonable to discuss workplace adjustments if the physical demands of your role are causing discomfort or concern, particularly during the first trimester.

Possible adjustments could include:

  • Taking regular seated breaks
  • Using a stool for tasks that do not require standing
  • Alternating between different duties
  • Asking a colleague to assist with heavier tasks
  • Wearing supportive and comfortable footwear

Workplace changes should be based on your individual circumstances and advice from your healthcare professional rather than fear created by a single study.

What does this mean for people who have experienced miscarriage?

Research findings about miscarriage risk can be distressing, particularly for someone who has recently experienced a pregnancy loss.

According to A/Prof Alex Polyakov, the findings should be interpreted with caution. While the study found an association between some workplace activities and miscarriage, it does not establish that bending, walking or standing causes miscarriage.

In most cases, miscarriage could not have been prevented. It is unlikely to have occurred because someone walked, stood, bent forward, exercised or continued working. Most miscarriages are caused by chromosomal abnormalities or other factors outside a person's control.

Anyone concerned about their risk, workplace duties or physical activity during pregnancy should speak with their GP, obstetrician or fertility specialist for individual advice.

About the authors

Alex Polyakov

Dr. Alex Polyakov

Medical Director Melbourne City and Fertility Specialist MBBS, MClinEpid, MReproMed, MHlth&MedLaw, MBioeth, GradCertEBM, FACLM, FANZCOG

Melbourne Fertility Specialist A/Prof Alex Polyakov at Genea. Complete fertility care from IVF to delivery, combining clinical expertise & academic research.

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