Drinking in moderation does not appear to have an adverse effect on a woman’s ability to conceive, a prospective cohort study from Denmark has found.

A total of 6,120 women, aged 21-45 years, who were trying to become pregnant and not receiving fertility treatment were followed up. Participants completed a baseline questionnaire and bimonthly follow-up questionnaires for 12 months or until they became pregnant.

The researchers used a statistical model to estimate fecundability ratios representing the cycle-specific probability of conception among women exposed to alcohol divided by that among non-drinking women.

A fecundability ratio below one indicated reduced fertility for women exposed to alcohol compared with those not exposed.

They also assessed the association between time to pregnancy and total alcohol consumption.

In total, 4,210 (69%) of the 6,120 participants achieved a pregnancy during the follow-up period.

At baseline, median alcohol intake was 2.0 standard measures of alcohol per week. (A standard measure was taken as 330 ml regular beer, 120 ml wine or 20 ml spirits).

Compared with no alcohol use, the adjusted fecundability ratios for consumption of one to three, four to seven, eight to 13, and 14 or more measures of alcohol a week were: 0.97 (95% CI: 0.91-1.03), 1.01 (95% CI: 0.93-1.10), 1.01 (95% CI: 0.87-1.16), and 0.82 (95% CI: 0.60-1.12), respectively.

Compared with no alcohol intake, the adjusted fecundability ratios for women who consumed only wine (≥ 3 measures), beer (≥ 3 measures), or spirits (≥ 2 measures) were 1.05 (95% CI: 0.91-1.21), 0.92 (95% CI: 0.65-1.29), and 0.85 (95% CI: 0.61-1.17), respectively.

The results did not show a reduction in fertility at lower levels of consumption (1-13 measures a week). The highest level (≥ 14 measures a week) was associated with an 18% reduction in fecundability compared with no alcohol use, although the confidence interval was wide.

There were no appreciable differences in the associations between beer and wine consumption, while the association between consumption of spirits and reduced fecundability was only slightly stronger.

While women who drink moderately may not have to achieve abstinence in order to maximise their fertility, ongoing consumption must be balanced against the possible harm of drinking during an early or unknown pregnancy. Those drinking more heavily, or binge drinking, while trying to conceive should be advised to reduce consumption.

Dr Jez Thompson

Mikkelsen EM, Riis AH, Wise LA et al. Alcohol consumption and fecundability: prospective Danish cohort study. BMJ 2016;354:i4262