Women referred for occupational risk assessment in pregnancy have no increased risk of adverse obstetric outcomes.

Introduction: Our aim was to study the association between pregnant women's referral status for occupational risk assessment, and their risk of preterm delivery (< 37 weeks), low birth weight (LBW) (< 2,500 g) and small for gestational age (SGA).

Methods: In a cohort study, 1,202 deliveries among pregnant women referred to two Danish clinics of occupational medicine (Copenhagen and Aarhus) from 1984 to 2010 were compared with the referred women's 1,077 non-referred pregnancy outcomes and with the pregnancy outcomes of 345,467 gainfully employed women from the same geographical areas and time period. Logistic regression was used to calculate odds ratios (OR) with 95% confidence intervals (CI). Calculations were adjusted for the mother's age at delivery, parity, ethnicity, socioeconomic status, smoking, and in supplementary analyses for year of birth.

Results: Referred women gave birth to children with a higher birth weight than the average employee (difference 47.8 g; 95% CI: 19.9-75.6), but the outcomes did not differ with respect to gestational age (difference 0.05 weeks; 95% CI: -0.06-0.17), preterm delivery (OR: 0.8; 95% CI: 0.62-1.04), LBW (OR: 0.81; 95% CI: 0.52-1.26) or SGA (OR: 0.92; 95% CI: 0.72-1.17).

Conclusion: The women who are referred for occupational risk assessment at two large occupational university departments are not at an increased risk of preterm birth or of delivering low birth weight children. This may reflect that reproductive hazards in Danish workplaces are limited and/or that the occupational risk assessment and counselling of pregnant women are preventing these selected adverse pregnancy outcomes.

Funding: The Research Unit at Department of Occupational and Environmental Medicine at Bispebjerg Hospital supported the study financially.

Trial Registration: not relevant. The study was conducted using systematically collected data including the refereed women's occupational exposure codes, which were anonymised and linked to national registries at Statistic Denmark. The Danish Data Protection Agency approved the study (R. no. 2012-41-1267).