8290474 Relative risk and excess fraction of adverse pregnancy outcomes across maternal occupation during pregnancy: a Danish nationwide register cohort study

<h3>Objective</h3> We aim to examine the associations between maternal occupation during pregnancy and risk of preterm birth, low birth weight and major congenital malformations of the offspring. <h3>Material and Methods</h3> We identified our study population of live singleton births from April 1, 2004 to December 31, 2018 using the DOC*X-Generation Cohort, which was created by linking several national registers with detailed information on employment and birth outcomes and covers all residents in Denmark. We will estimate relative risks for the adverse birth outcomes by occupation and industry. Additionally, we will estimate excess fractions, defined as the proportion of adverse birth outcomes that would not have occurred if each occupation and industry group had the same risk as the lowest-risk group, after adjusting for relevant covariates and within-group random variation. Logistic regression will be used, firstly, to test the null-hypotheses and, secondly, to estimate group-specific expected numbers of cases under the null-hypotheses of no risk inequalities. Excess fractions will be estimated using Monte Carlo simulation. <h3>Results</h3> We plan to share the results for all three outcomes. For now, job codes have been grouped into 37 occupational groups based on the Danish version of ISCO-88 and 36 industrial groups using the Danish Working Environment Authority’s classification. Out of the included study populations of approximately 630.000 pregnancies, we have identified 29.624 cases of preterm birth, 6.106 cases of low birth weight among term births and 27.636 cases of major congenital malformations. <h3>Conclusion</h3> The analyses will show if there are disparities in these adverse birth outcomes across maternal occupations and industries registered for pregnant women giving birth in Denmark, 2004-2018. Findings can provide updated valuable insights into how specific occupations and industries affect pregnancy and health in a high-income society with relatively high occupational health standards. <h3>Funding</h3> Working Environment Research Fund (Project J.nr. 20225100773).