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Occupational exposure during pregnancy and the risk of hay fever in 7-year-old children


  • Authorship and contributorship

    Berit Hvass Christensen: Selection of data from Danish National Birth Cohort (DNBC), performing statistical analyses, writing of article text and tables. Ane Marie Thulstrup: Supervision of statistical analyses, revision of article text. Kirsten Skamstrup Hansen: Revision of text. Lars Rauff Skadhauge: Revision of text. Karin Sørig Hougaard: Revision of text. Vivi Schlünssen: Main reviser of text and tables.

  • Ethics

    All participants from the DNBC provided written consent. The study was approved by all of the scientific ethics committees in Denmark and by the Danish Data Protection Board.

  • Conflict of interest

    The authors have stated explicitly that there are no conflicts of interest in connection with this article.


Berit Hvass Christensen, MD, Section of Environmental and Occupational Medicine, Department of Public Health, Aarhus University, Bartholins Allé 2, Bg 1260, 8000 Aarhus C, Denmark.

Tel: +45 8942 6153

Fax: +45 8942 6199




The prevalence of allergic diseases including hay fever has increased in the last decades, especially in Westernised countries. The aim of this study was to analyse whether occupational exposure during pregnancy is associated with development of hay fever in 7-year-old Danish children.


A total of 42 696 women and their children from the Danish National Birth Cohort were categorised according to maternal occupational exposure. Exposure information was obtained by combining job title in pregnancy with a commonly used asthma Job Exposure Matrix. Information on hay fever in the child was obtained by an internet questionnaire at follow-up at 7 years of age.


Adjusted logistic regression analyses showed no significant association between maternal occupational exposure during pregnancy and hay fever among the 7-year-old children. Stratifying for atopic status in the children did not change the results. The prevalence of hay fever was 10.0% in the atopic children compared with 3.6% in the non-atopic children. Maternal atopic disposition increased the risk of hay fever in the offspring, odds ratio (OR) 2.49 [95% confidence interval (CI) 2.26; 2.74]. Rural residence during pregnancy decreased the risk for hay fever [OR 0.74 (95% CI 0.59; 0.92)] as did parity, OR 0.72 (95% CI 0.66; 0.80) and 0.70 (95% CI 0.48; 1.00) for 2nd and 3rd child, respectively, compared with the firstborn child.


The results suggest that occupational exposure among pregnant women in Denmark is not a risk factor for hay fever among young children.