Smoking and female infertility: a systematic review and meta-analysis

The high prevalence of smoking among women in their reproductive yearscontinues to be a matter of concern. The negative effects of smoking ongeneral health are well known, but smoking may also affect fertility. Theobjective of the present study was to perform a systematic review of theliterature to determine whether there is an association between smoking andrisk of infertility in women of reproductive age, and to assess the size ofthis effect. In the 12 studies used for this meta- analysis, the overallvalue of the odds ratio (OR) for risk of infertility in women smokersversus non-smokers was 1.60 [95% confidence interval (CI) 1.34-1.91].Studies of subfertile women undergoing in-vitro fertilization (IVF)treatment also show a reduction in fecundity among women smokers. Ameta-analysis of nine studies found an OR of 0.66 (95% CI 0.49-0.88) forpregnancies per number of IVF- treated cycles in smokers versusnon-smokers. Despite the potential limitations of meta-analyses ofobservational studies, the evidence presented in this review is compellingbecause of the consistency of effect across different study designs, samplesize and types of outcome. However, continued reassurance is needed thatthe calculated overall effect is not in fact due to confounding variables.