Cigarette smoking may affect meiotic maturation of human oocytes.

There is a strong association between cigarette smoking and reduced fecundity, reduced fertility, and early mean age of menopause, suggesting that smoking may impair oocyte function and viability. We analysed the effect of smoking on meiotic maturation of oocytes. A total of 156 women undergoing in-vitro fertilization therapy, classified as non-smokers (n = 102), passive smokers (n = 21), light smokers (< 15 cigarettes/day; n = 19), and heavy smokers (> or = 15 cigarettes/day, n = 14), participated in this study. Tubal factor infertility was more frequent in smokers, in agreement with the literature, and showed a significant dose effect (P = 0.008). Smokers had decreased numbers of retrieved oocytes compared with non-smokers, suggesting reduced fertility. Cytogenetic data from 286 oocytes apparently unfertilized showed similar proportions of haploid (normal) and aneuploid chromosome complements among groups. In contrast, oocytes with diploid complements were more frequent among smokers. Regression of individual proportions of diploid oocytes on number of cigarettes smoked per day was very significant (P = 0.0003). The increased frequency of oocyte diploidy in smokers, probably resulting from prevention of first polar body extrusion, indicates meiotic immaturity. Also, triploid zygotes occurred more frequently in smokers (P = 0.03), suggesting preferential digynic fertilization. Our study shows that external factors, like cigarette smoking, may be hazardous to the viability and function of developing oocytes and their resulting embryos.