Smoking and decreased fertilisation rates in vitro.

To examine possible mechanisms for the association between cigarette smoking and reduced fertility, we have measured the concentration of the nicotine metabolite cotinine in ovarian follicular fluid collected at the time of oocyte recovery during treatment for in-vitro fertilisation. In a group of women in whom follicular fluid cotinine could not be detected (limit of accurate measurement 20 ng/ml) 116 oocytes were collected, of which 84 became fertilised (72%), whereas among women with cotinine concentration greater than 20 ng/ml 20/45 (44%) oocytes did so (p < 0.01). The median fertilisation rates for individuals (range 1-8 eggs each) in the high and low cotinine groups were 57% and 75%, respectively (p < 0.05). These findings suggest that infertile women should be advised to stop or reduce smoking generally, and especially before treatment by in-vitro fertilisation.