Objective: To examine the effect of alcohol consumption on the probability of conception.
Design: A follow up study over six menstrual cycles or until a clinically recognised pregnancy occurred after discontinuation of contraception.
Subjects: 430 Danish couples aged 20-35 years trying to conceive for the first time.
Main outcome measures: Clinically recognised pregnancy. Fecundability odds ratio: odds of conception among exposed couples divided by odds among those not exposed.
Results: In the six cycles of follow up 64% (179) of women with a weekly alcohol intake of less than five drinks and 55% (75) of women with a higher intake conceived. After adjustment for cycle number, smoking in either partner or smoking exposure in utero, centre of enrolment, diseases in female reproductive organs, woman's body mass index, sperm concentration, and duration of menstrual cycle, the odds ratio decreased with increasing alcohol intake from 0.61 (95% confidence interval 0.40 to 0.93) among women consuming 1-5 drinks a week to 0.34 (0.22 to 0.52) among women consuming more than 10 drinks a week (P=0.03 for trend) compared with women with no alcohol intake. Among men no dose-response association was found after control for confounders including women's alcohol intake.
Conclusion: A woman's alcohol intake is associated with decreased fecundability even among women with a weekly alcohol intake corresponding to five or fewer drinks. This finding needs further corroboration, but it seems reasonable to encourage women to avoid intake of alcohol when they are trying to become pregnant.
PIP: The effect of alcohol consumption on the probability of conception was investigated in a prospective study of 430 Danish couples seeking to achieve pregnancy for the first time. Couples were recruited through a national mailing to trade union members and followed for six menstrual cycles after contraception discontinuation or until a clinically recognized pregnancy occurred. Mean weekly alcohol intake was 4.0 drinks among women and 9.5 drinks among their male partners; 73 women (17%) abstained from alcohol drinking throughout the six cycles. During the study period, 179 (64%) of the 280 women with an average weekly alcohol intake of less than five drinks and 75 (55%) of the 136 women with a higher intake conceived. Among male partners, these rates were 67% and 58%, respectively. After adjustment for cycle number, smoking, enrollment center, diseases of the reproductive system, body mass index, sperm concentration, and menstrual cycle duration, the odds ratio decreased with increasing alcohol consumption from 0.61 (95% confidence interval, 0.40-0.93) among women who consumed 1-5 drinks a week to 0.55 (95% CI, 0.36-0.85) among those reporting 6-10 drinks a week to 0.34 (95% CI, 0.22-0.52) among women consuming 11-15 drinks a week compared with women with no alcohol intake. No dose-response relationship was found in male partners after adjustment for the same confounders. Although these findings require further corroboration, they suggest that even moderate alcohol consumption has a significant adverse effect on fecundability.