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Occupational lifting of heavy loads and preterm birth: a study within the Danish National Birth Cohort
  1. Stine Bjerrum Runge1,
  2. Jacob Krabbe Pedersen2,
  3. Susanne Wulff Svendsen3,
  4. Mette Juhl1,
  5. Jens Peter Bonde4,
  6. Anne-Marie Nybo Andersen1
  1. 1Section of Social Medicine, Department of Public Health, University of Copenhagen, Copenhagen K, Denmark
  2. 2Division of Epidemiology, Institute of Public Health, University of Southern Denmark, Odense, Denmark
  3. 3Department of Occupational Medicine, Danish Ramazzini Center, Herning Hospital, Herning, Denmark
  4. 4Department of Occupational and Environmental Medicine, Bispebjerg University Hospital, Copenhagen NV, Denmark
  1. Correspondence to Professor Anne-Marie Nybo Andersen, Section of Social Medicine, Department of Public Health, University of Copenhagen, Oster Farimagsgade 5, Box 2099, Copenhagen K DK-1014, Denmark; amny{at}


Objectives To examine the association between occupational lifting during pregnancy and preterm birth. The risk of preterm birth was estimated for total burden lifted per day and number of medium and heavy loads lifted per day.

Methods In a study population of 62 803 pregnant women enrolled to the Danish National Birth Cohort from 1996 to 2002, the association between self-reported occupational lifting in the first part of pregnancy and preterm birth was analysed using logistic regression models with adjustment for age, parity, cervical cone biopsy, assisted reproduction and smoking. Associations between lifting and extremely (before 28 weeks), very (28–32 weeks) and moderately (33–37 weeks) preterm birth were analysed using Cox regression models.

Results We found a dose–response relation between total daily burden lifted and preterm birth with an OR of 1.50 (95% CI 1.03 to 2.19) with loads over 1000 kg/day. No threshold value was found. The associations were strongest for extremely and very preterm birth with HRs (95% CIs) of 4.3 (1.4 to 13.8) and 1.7 (0.7 to 4.0), respectively. Lifting heavy loads (>20 kg) more than10 times/day was associated with preterm birth up to an OR of 2.03 (95% CI 1.14 to 3.62).

Conclusion In a society with social welfare and a highly regulated working environment, occupational lifting was associated with an increased risk of preterm birth.

  • Epidemiology
  • Lifting
  • Preterm birth
  • Reproduction

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