Adult and Prenatal Exposures to Tobacco Smoke as Risk Indicators of Fertility among 430 Danish Couples

The effect of male and female current smoking and smoking exposure in utero on fecundability was investigated in a prospective cohort study conducted in 1992-95 in Aarhus and Copenhagen Denmark. From a nationwide mailing to 52255 trade union members who were 20-35 years old lived with a partner and had no children a total of 430 couples were recruited. Couples discontinued contraception at study enrollment and were followed for 6 menstrual cycles or until pregnancy. A logistic regression model was used with pregnancy outcome of each cycle in a Cox discrete model calculating the fecundability odds ratio. 127 women (30%) and 137 men (32%) were smokers at study enrollment; 163 women (42%) and 154 men (40%) reported exposure to cigarette smoke in utero. In the 6 cycles of follow-up 51.2% of smokers and 63.0% of nonsmokers conceived. After adjustment for female body mass index and alcohol intake female reproductive organ diseases semen quality and duration of the menstrual cycle the fecundability odds ratio (OR) for smoking women exposed in utero was 0.53 (95% confidence interval (CI) 0.31-0.91) compared with unexposed smokers. The fecundability OR for nonsmoking women exposed in utero was 0.70 (95% CI 0.48-1.03) and that for female smokers not exposed in utero was 0.67 (95% CI 0.42-1.06). In utero exposure was also associated with a decreased fecundability OR in men (0.68; 95% CI 0.48-0.97) but current smoking did not reduce fecundability significantly. These findings indicate cigarette smoking is a reproductive health hazard both before and during pregnancy.