Women who have high alcohol intake, 14 or more servings of alcohol a week are slightly more likely to have reduced fertility, suggests a study published in The BMJ today.
In developed countries, up to 24% of couples experience infertility, defined as time to pregnancy of 12 months or more. Official guidelines in countries like the USA, UK and Denmark recommend that women trying to become pregnant should abstain from alcohol consumption. But the extent to which alcohol intake affects female fertility is unclear. So a group of Danish researchers carried out a large prospective cohort study to examine the association between pre-conception alcohol consumption and time to pregnancy.
In total, 6,120 female Danish residents, aged 21-45 years, were included in the study. They were all in a stable relationship with a male partner, trying to conceive and not receiving fertility treatment, between June 2007-January 2016. The study assessed overall alcohol consumption as well as intake of specific types of alcoholic beverages, including beer, wine, and spirits.
Alcohol consumption was self reported as beer (330 mL bottles), red or white wine (120 mL glasses), dessert wine (50 mL glasses), and spirits (20 mL), and was categorized in standard servings per week (none, 1-3, 4-7, 8-13, and 14/more).
Each female participant completed bimonthly questionnaires for 12 months, or until conception occurred, on alcohol use, pregnancy status, menstrual cycles, frequency of intercourse, and smoking.
In women who drank 14 or more servings of alcohol a week, there were 37 pregnancies in 307 cycles, compared with 1381 pregnancies in 8054 cycles in women who did not drink.
While the sample size was large, only 1.2% of women drank more than 14 servings of alcohol a week, so the estimate for this high level of exposure is imprecise, caution the authors.
This is an observational study, so no firm conclusions can be made about cause and effect, and low to moderate intake of alcohol seemed to have no effect on women's fertility, nor did the type of alcohol beverage consumed. Regardless of their own data the authors say couples should abstain from alcohol during their fertile window until a pregnancy is ruled out. They believe the fetus may be particularly vulnerable to alcohol during the first few weeks after conception.