Parent's Occupation and Isolated Orofacial Clefts in Norway: A Population-based Case-control Study

Purpose: Occupational factors have been associated with risk of orofacial clefts in offspring, although data are limited. We explored associations between parent's occupation and isolated orofacial clefts using a population-based case-control study. Methods: Cases were restricted to infants born with an isolated orofacial cleft in Norway during the period 1996 to 2001 (314 with cleft lip with or without palate [CLP] and 118 with cleft palate only [CPO]). Controls (n = 763) were chosen randomly from all Norwegian live births. We considered full-time employment during the first 3 months of pregnancy. Results: Several maternal occupations previously associated with clefts showed some evidence of association, including hairdressers (CLP; adjusted odds ratio = 4.8; 95% confidence interval [CI]: 0.99-23). Mothers working in manufacturing and in food production had increased odds for babies with CPO (3.8; 1.3-11, and 7.1; 1.5-33, respectively). Among fathers' occupations previously associated with clefts, an association was suggested for woodworking both for CLP (1.7; 0.85-3.2) and for CPO (2.0; 0.82-4.7). Fathers working as professional housekeepers showed substantial increased odds of CPO (12; 3.3-46). Conclusions: Taken together with previous studies, these results suggest that exposures in certain occupations may influence the risk of orofacial clefting in offspring. Specific exposures accompanying these occupations warrant exploration.