O-325 PHYSICAL WORK DEMANDS DURING PREGNANCY AND THE RISK OF PRETERM BIRTH – FINDINGS FROM A DANISH REGISTER-BASED COHORT STUDY

Abstract Introduction The objective of this study was to corroborate or refute earlier indications that high workload in pregnancy is associated with preterm birth. Methods The register-based cohort, DOC*X-Generation, included all working pregnant women and their liveborn children in Denmark (1977-2018). Register-data contributed information of gestational age used to define preterm (22-36 gestational week) and extremely preterm (22-32 gestational week) births, and occupational codes during pregnancy – DISCO-88. A Job exposure matrix (JEM) provided information on occupational exposure for each occupation and not individually. Workload was provided by the JEM, physical work demands (Work Environment and Health, Denmark), which assigned each woman with an exposure value based on DISCO-88 occupational codes. Other nationwide registers provided potential confounders. Results The preliminary findings included 1,201,974 women working during pregnancy; of which 4.3% gave birth preterm. Employment in occupations with high physical work demands during pregnancy was associated with a small increased risk of preterm birth (highest exposed group, adjusted OR=1.10 (95% CI 1.06-1.13)) and extremely preterm birth (highest exposed group, adjusted OR=1.15 (95% CI 1.07-1.23)). There was a tendency towards an exposure-response relationship for both outcomes. Discussion Strengths include a non-selected cohort of working women over a 40-year period, including potential confounders, e.g., maternal country of origin and education. One limitation is that the JEM is only based on data from 2012 and 2014, and therefore does not reflect potential changes in physical workload over time. Conclusion This study supports the previous findings of an increased risk of preterm birth due to physical workload during pregnancy.