Infertility is a common condition that is increasing in incidence. Alcohol consumption has been implicated as a contributory factor. Women with high alcohol intake have increased rates of menstrual disorders, miscarriages, stillbirths, preterm deliveries and placental abruption. Heavy consumption of alcohol is also known to have teratogenic effects. Retrospective studies have found that a high intake of alcohol is associated with reduced fertility in women, but the effect of moderate alcohol intake is unknown. Jensen and colleagues examined the effect of alcohol consumption in couples trying to conceive to prospectively establish the relationship between alcohol intake and fertility.

A total of 430 Danish couples who were trying to conceive for the first time were enrolled in the study when they discontinued use of birth control and were followed for six menstrual cycles or until a pregnancy was confirmed. Couples completed an extensive initial questionnaire on medical, demographic, reproductive and lifestyle factors. Each man provided a semen sample at the beginning of the study and during each of his partner's menstrual cycles. Each woman recorded vaginal bleeding and frequency of intercourse on a daily basis. Tobacco, alcohol and caffeine intake were recorded regularly during the study.

No alcohol intake during all cycles was reported by 73 (17 percent) of the women. Among the women who consumed alcohol, the mean weekly alcohol intake was four drinks. Ten percent of men reported drinking no alcohol; the mean weekly alcohol intake for men who drank was 9.5 drinks. Alcohol intake was associated with their own and their partners' use of cigarettes and caffeine. Among the 280 women who reported drinking less than five drinks per week, 179 (64 percent) conceived within six cycles. Among the 136 women reporting higher intake, 75 (55 percent) conceived in the same time span. Among the men, the comparable figures were 67 percent and 58 percent, respectively. The authors calculated that the adjusted odds ratio for women consuming up to five drinks per week was 0.61, compared with women who reported no alcohol intake. For women consuming more than 10 drinks per week, the adjusted odds ratio was 0.34. No dose-response relationship could be demonstrated for men in this study.

The authors conclude that fecundity is reduced in women who consume alcohol, even in women who have fewer than five alcoholic drinks per week. They encourage women who are trying to conceive to avoid drinking alcohol.