Occupational Noise Exposure During Pregnancy and Birth Outcomes: A Large-Scale Cohort Study in Nordic Countries.

OBJECTIVES: Adverse birth outcomes such as low birth weight (LBW), small for gestational age (SGA) and preterm birth (PTB), are major indicators of perinatal health, yet evidence on the effects of occupational noise during pregnancy remains limited. METHODS: This multi-country register-based study (n=590,454) examined associations between occupational noise exposure estimated using a job-exposure matrix with daily 8-hour equivalent sound levels (<70, ≥70-<75, ≥75-<80, ≥80 dBA) and adverse birth outcomes in metropolitan areas of Denmark, Finland, Norway, and Sweden. RESULTS: Results across the four countries were inconsistent. Indications of higher odds of LBW, SGA, and PTB, particularly in Norway and Sweden were seen, though these associations attenuated after full adjustment. Meta-analyses of fully adjusted models indicated no pooled associations between occupational noise exposure (≥80 dBA category) and birth weight (estimate = -0.35 g, 95% CI [-14.58, 13.88]), LBW (OR = 1.03, 95% CI [0.88, 1.20]), SGA (OR = 1.07, 95% CI [0.88, 1.29]), or PTB (OR = 1.01, 95% CI [0.83, 1.23]). However, sensitivity analyses based on the Swedish data suggested that working hours (full-time, part-time) and work absence may modify the association (birth weight: estimate = -37.66 g, 95% CI [-61.11, -14.22], LBW: OR = 1.49, 95% CI [1.22, 1.81], PTB: OR = 1.44, 95% CI [1.23, 1.70]). CONCLUSIONS: Overall, the findings do not support strong associations between occupational noise exposure and adverse birth outcomes. Based on sensitivity analysis, additional data on working hours and work absence may modify the relationship in future studies.