First trimester employment, working conditions and preterm birth: a prospective population-based cohort study

Occup Environ Med. 2021 Sep;78(9):654-660. doi: 10.1136/oemed-2020-107072. Epub 2021 Feb 24.


Objectives: To explore the association between working conditions during first trimester and total preterm birth (PTB), and subtypes: spontaneous PTB and iatrogenic PTB, additionally to explore the role of hypertension.

Methods: Pregnant women from the Amsterdam Born Children and their Development study, filled out a questionnaire between January 2003 and March 2004, two weeks after first prenatal screening (singleton liveborn, n=7561). Working conditions were working hours/week, standing/walking hours/week, physical work load and job strain.

Results: Prolonged standing/walking during first trimester was associated with an increased risk for total PTB (OR=1.5; 95% CI 1.0-2.3, after adjustments). Other working conditions were not related to total PTB. The separation into spontaneous and iatrogenic PTB revealed that standing/walking was associated with iatrogenic PTB only (OR=2.09; 95% CI 1.00-4.97). The highest risk was found for the combination of a long workweek with high physical work load (OR=3.42; 95% CI 1.04-8.21). Hypertension did not mediate these associations; however, stratified analysis revealed that high physical work load was only related to iatrogenic PTB when pregnancy-induced hypertension was present (OR=6.44; 95% CI 1.21-29.76).

Conclusion: This study provides evidence that high physically demanding work is associated with an increased risk for iatrogenic PTB and not with spontaneous PTB. Pregnancy-induced hypertension may play a role: when present, high physical work load leads to a more severe outcome.

Keywords: occupational health; occupational stress; pregnancy outcome; public health; workload.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Employment / statistics & numerical data*
  • Female
  • Humans
  • Netherlands / epidemiology
  • Pregnancy
  • Pregnancy Trimester, First*
  • Premature Birth / epidemiology*
  • Premature Birth / etiology
  • Prospective Studies
  • Risk Factors
  • Surveys and Questionnaires
  • Workload / statistics & numerical data
  • Workplace / statistics & numerical data