Occupational Physical Activity Linked to Increased Miscarriage Risk, Danish Study Finds
A large-scale Danish study has identified associations between specific occupational physical activities—particularly forward bending and walking—and an elevated risk of miscarriage.
Each additional hour of forward bending at a 30-degree angle was associated with a 36% higher risk of miscarriage.
Key Findings
The study analyzed data from 475,312 women encompassing 803,829 pregnancies. The results show a clear dose-response relationship for forward bending:
- Forward bending: Each additional hour linked to a 36% higher risk of miscarriage
- Walking: Each additional hour associated with an 18% higher risk
- Standing: Each additional hour tied to a 3% higher risk
Researchers noted that the dose-response relationship was consistent only for forward bending.
Background
Miscarriage affects approximately 15% of women. Known risk factors include:
- Parental age
- Smoking
- Night shift work
- Exposure to air pollution and chemicals
Previous studies on occupational physical activity have been inconclusive, making this new research particularly significant.
Study Details
The researchers employed a pregnancy-specific job exposure model that combined activity tracker readings with expert evaluations. Data was drawn from Danish national registers covering pregnancies between 2004 and 2018.
Among the pregnancies studied, 81,307 (just over 10%) ended in miscarriage. The researchers note this rate is lower than usual, possibly because many early miscarriages are not recorded in hospital data.
Limitations
The study is observational and cannot establish causation. The authors acknowledge lacking individual-level data on:
- Smoking
- Lifting
- Shift work
- Chemical exposures
Forward bending is relatively uncommon in most jobs, so overall impact may be limited despite the higher risk estimates.
Recommendations
The researchers suggest these occupational activities may affect placental perfusion or hormonal regulation. They highlight the absence of formal guidelines in Denmark addressing standing, walking, or forward bending in early pregnancy, and call for including early pregnancy in occupational guidelines.
"Despite higher risk estimates, forward bending is relatively uncommon in most jobs, so overall impact may be limited."