Reproductive disorders in hairdressers and cosmetologists: a meta-analytical approach.

OBJECTIVES The aim of this study was to perform a systematic review and to use a meta-analytical approach to assess quantitatively the risk of adverse pregnancy outcomes in hairdressers and cosmetologists. METHODS A systematic literature search up to 1 February 2012 was carried out using major bibliographic databases, grey literature, contacts with research teams working on the subject, review papers and reference lists of selected articles. Observational studies reporting measures of effects in relation with body care (hairdressers, cosmetologists, etc.) and reproductive disorders were included. Study quality was assessed by three reviewers. The estimated risk ratios (RR) from all studies reporting on identical outcomes were combined using an average of logarithm transformation of estimated RR weighted by their inverted variance. Statistical heterogeneity across studies was assessed using Cochran's Q test. To explore the sources of heterogeneity, several sensitivity analyses and subgroup analyses were conducted based on study quality, country, study period, alcohol consumption, smoking habit, jobs and control populations. RESULTS Nineteen studies were selected and reviewed in-depth. The combined risk ratios (RRcs) of five reproductive outcomes were calculated and found to be significantly increased for four outcomes: time to pregnancy, which had an RRc of 1.11 (95% CI: 1.03-1.19); premature birth, which had an RRc of 1.05 (95% CI: 0.99-1.11); small for gestational age, which had an RRc of 1.24 (95 CI%: 1.10-1.41); low birth weight, which had an RRc of 1.21 (95% CI: 1.06-1.39); and embryonic and fetal losses, which had an RRc of 1.19 (95% CI: 1.03-1.38). CONCLUSIONS This work confirms a weak increase in risk of some reproductive disorders in female hairdressers/cosmetologists. However, the evidence level is rather weak, and a causal association between job and reproductive outcomes cannot be asserted.