Maternal occupational exposure to noise: prevalence, maternal effects and infant outcomes in the National Birth Defects Prevention Study, 1997-2011

Objectives We investigated associations between occupational noise and gestational diabetes mellitus, pregnancy-related hypertension (including pre-eclampsia/eclampsia), preterm birth and small for gestational age (SGA) infants. Methods Data were analysed for 7889 singleton, live-born infants without major birth defects or chromosomal disorders and their mothers from the National Birth Defects Prevention Study from 1997 to 2011. Typical maternal occupational noise exposure in all jobs held from 1 month prior to conception through the end of pregnancy was estimated by expert rater and categorised as quiet (<60 A-weighted decibels (dBA)), low (60-75 dBA), moderate (76-84 dBA) or loud (>85 dBA). Multiple logistic regression was used to estimate associations (adjusted ORs and 95% CIs) between noise exposure levels and outcomes. Results Approximately 77.4% of pregnant workers had quiet levels of occupational noise exposure, 11.0%, 10.1% and 1.5% had low, moderate and loud exposure levels, respectively. Compared with quiet levels of noise, pregnant workers exposed to low levels of noise had decreased odds of delivering an SGA infant (adjusted OR (aOR)=0.72; 95% CI 0.53 to 0.99) and those exposed to moderate levels had increased odds of delivering an SGA infant (aOR=1.37; 95% CI 1.05 to 1.77). No other significant associations were observed. Conclusion Maternal occupational noise exposure below the 85 dBA threshold recognised as hazardous may be associated with SGA among infants. Elevated point estimates (>1) were observed for the highest noise exposure category and all outcomes, though CIs were wide and statistical significance was not attained. Further research is warranted to address existing knowledge gaps.