Industrial differences in female fertility treatment rates--a new approach to assess differences related to occupation?

AIMS: Infertility is highly prevalent and 16-26% of women trying to achieve a pregnancy experience infertility in one or more periods. Several exposures in the work environment have been hypothesized to affect female reproduction. This study aimed to estimate relative rates (RR) of female fertility treatment in the 57 industrial groups in Denmark. METHODS: The closed cohort of all 20-39 year old economically active women in Denmark by January 2001 (n = 567,816) were followed-up for hospital contacts due to infertility from 2001 to 2005 as registered in the Danish Occupational Hospital Register. Age-standardized relative rates for being diagnosed as infertile were estimated by industry. Further standardization with respect to socioeconomic status was also performed. RESULTS: In total, 12,575 women were diagnosed with infertility during the follow-up period. Three industries presented with statistically significant elevations in age-standardized RRs: hospitals (RR = 1.27, 95% confidence interval (CI): 1.20-1.35), general and dental practice (RR = 1.17, 95% CI: 1.02-1.35) and other health care (RR = 1.24, 95% CI: 1.09-1.41). Standardization for socioeconomic status rendered two industries that were statistically significantly elevated: manufacture of wood and wood products (RR = 1.20, 95% CI: 1.02-1.42) and hospitals (RR = 1.17, 95% CI: 1.10-1.24). CONCLUSIONS: Interpretation of the results is complex, since the relative contributions to the observed inequalities of the work environment and, for example, differences in inclination to start a family or in proneness to seek treatment are difficult to resolve. Withstanding shortcomings and limitations, register data of fertility treatment offers a possibility to suggest industries for further investigation of reproductive health.