Background Several potential endocrine disrupting chemicals (EDCs) are suspected of adversely affecting pregnancy outcomes, but research is limited. Therefore, we aimed to investigate the effects of maternal occupational exposure to EDCs during pregnancy on birth weight and gestational age.

Methods The study was conducted among women participating in the PRegnancy and Infant DEvelopment (PRIDE) Study, a nationwide prospective cohort study in the Netherlands which follows women and their offspring from early pregnancy onwards using repeated web-based questionnaires. Based on the job information provided, the probabilities of exposure to EDCs during pregnancy were assessed using an EDC-specific job exposure matrix developed by our group in 2008, but adapted to the current occupational situation. Confounding-adjusted effect estimates for associations between EDC exposure and the outcome parameters birth weight and gestational age were calculated using linear regression analyses.

Results In total, 1285 out of 1369 women with a singleton pregnancy resulting in a live birth before May 1st 2015 were included in the analyses, in which we compared possibly and probably exposed women to non-exposed women for 10 different EDC categories. The mean birth weight was 3456 grams, almost exactly the population average. Infant birth weights were reduced by 191 (95% CI: 0–383) and 223 (95% CI: 27–420) grams after maternal exposure to ethylene glycol ethers and alkylphenolic compounds, respectively. Exposure to metals, in particular mercury, reduced birth weight by 334 (95% CI: 114–553) grams. In contrast, exposure to ethylene glycol ethers and alkylphenolic compounds seemed to prolong gestation by approximately 5 days. All results were adjusted for gestational age, lifestyle factors, pregnancy complications, and other occupational exposures.

Conclusion This study showed that maternal employment during pregnancy may adversely affect infant birth weight via occupational exposure to several EDCs, whereas the same exposures may prolong gestational age. However, all effect estimates were modest.