Women who drink heavily may experience a reduction in fertility, according to a new Danish study published in the British Medical Journal (BMJ).
The findings show that female study participants who consumed 14 or more alcoholic beverages per week were about 18 percent less likely to become pregnant. However, low to moderate consumption of alcohol — one to seven servings a week — appeared to have no effect on women’s fertility, nor did the type of alcohol beverage consumed.
In developed countries, up to 24 percent of couples experience infertility, defined as taking 12 months or more to become pregnant. While it is typically recommended that women avoid alcohol consumption while trying to become pregnant, the extent to which alcohol affects female fertility was unclear.
To find some answers, researchers at the University Hospital of Aarhus in Denmark conducted a large study to examine the association between pre-conception alcohol consumption and time to pregnancy.
The study involved 6,120 female Danish residents, aged 21-45 years. All of the participants were in a stable relationship with a male partner, trying to conceive and not receiving fertility treatment, between the dates of June 2007 to January 2016.
The researchers 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 (approximately 11 oz bottles), red or white wine (4 oz glasses), dessert wine (1.6 oz glasses), and spirits (.67 oz), and was categorized in standard servings per week (none, 1-3, 4-7, 8-13, and 14/more).
Each female participant filled out 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.
Even though the sample size was large, only 1.2 percent 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. Furthermore, since this was an observational study, no firm conclusions can be made about cause and effect.
The study did not distinguish between regular and binge drinking, which is important because alcohol can affect the menstrual cycle. And the male partner’s alcohol intake was not measured, which is known to affect sperm quality.
The researchers suggest that couples who are trying to conceive abstain from drinking alcohol during their fertile window, because the developing fetus may be particularly vulnerable to alcohol during the first few weeks after conception.
In a linked editorial, epidemiologist Dr. Annie Britton from University College London said the results “offer some reassurances” to couples trying to get pregnant and suggests that “total abstinence may not be necessary to maximize conception rates” because “if alcohol is consumed moderately, it seems that this may not affect fertility.”
“However, it would be wise to avoid binge drinking, both for the potential disruption to menstrual cycles and also for the potential harm to a baby during early pregnancy. If a couple are experiencing difficulty in conceiving, it makes sense for both partners to cut down on their alcohol intake,” she concluded.