Alcohol consumption is linked to reduced chances of pregnancy

A study of associations between alcohol consumption and the chances of getting pregnant suggests that women who wish to conceive should avoid drinking too much alcohol. In the second half of the menstrual cycle, even moderate consumption is linked to reduced chances of pregnancy.

The study, published today in Human reproduction, one of the world’s leading reproductive medicine journals, studied alcohol use and fertility, which is defined as the likelihood of conceiving in a single period cycle. This is the first study to look at this based on the different phases of women’s menstrual cycles.

The researchers led by Dr. Kira Taylor, associate professor of epidemiology and population health at the School of Public Health and Information Studies at the University of Louisville, Kentucky, analyzed data from the Mount Sinai study on female office workers. Women aged 19 to 41 were recruited between 1990 and 1994 and followed for up to 19 menstrual cycles. The women filled out daily diaries indicating how much and what type of alcohol they drank, and they provided urine samples on the first and second day of each menstrual cycle to check for pregnancy.

Binge drinking was defined as more than six alcoholic beverages one week, moderate alcohol consumption was three to six drinks per week, and binge drinking was defined as four or more drinks in a single day. Each drink consisted of a third of a liter of beer (355 milliliters), an average glass of wine (148 milliliters), or just under a double shot of spirits (44 milliliters). The researchers gathered information on factors that could affect the results, such as age, medical history, smoking, obesity, use of birth control methods, and intention to become pregnant. Data on 413 women were available for the present study.

Dr Taylor said: “We have found that heavy drinking during any phase of the menstrual cycle was significantly associated with a reduced likelihood of conception compared to non-drinkers. This is important because some women who are trying to conceive might believe that it is “safe” to drink during certain parts of the menstrual cycle.

“During the luteal phase, which is the last two weeks of the menstrual cycle before the onset of bleeding and when the implantation process occurs, not only heavy alcohol consumption, but also moderate alcohol consumption was significantly associated at a reduced probability of conception.

“At the time of ovulation, usually around day 14 of the cycle, consuming a lot of alcohol, whether it was binge drinking or binge drinking, was significantly associated with reduced chances of conception. “

Compared with non-drinkers, moderate and excessive drinking during the luteal phase was linked to a reduction in the chances of conceiving by approximately 44%. Heavy alcohol consumption during the ovulatory part of the cycle was also associated with a significant 61% reduction in the chances of getting pregnant. However, the researchers stress that these are only estimates and should be treated with caution.

“If we assume that a typical, healthy, non-drinking woman in the general population trying to conceive has about a 25% chance of conceiving in a menstrual cycle, then out of 100 women about 25 non- drinkers would conceive in a particular cycle, about 20 moderate drinkers would conceive and only about 11 heavy drinkers would conceive, “said Dr Taylor.” But the effect of moderate drinking during the luteal phase is more pronounced and only about 16 moderate drinkers would design.

“Our study only involved a few hundred women and while we believe the results strongly suggest that high and even moderate alcohol consumption affects the ability to conceive, the exact percentages and numbers need to be considered. as rough estimates. “

Each additional day of binge drinking was associated with an approximately 19% reduction in the chance of conceiving during the luteal phase and a 41% reduction during the ovulatory phase. The researchers found no difference in their results between the different types of drinks.

The study cannot show that alcohol consumption reduces the chances of getting pregnant, only that it is associated with it. Possible biological mechanisms that could explain the association could be that alcohol consumption affects the processes involved in ovulation so that no eggs are released during the ovulatory part of the cycle, and that alcohol could affect the ability of a fertilized egg to implant in the uterus.

Dr Taylor said: “This is the first study to examine the effect of alcohol on fertility during specific phases of the menstrual cycle, using daily data on alcohol and other factors. important factors such as smoking and unprotected sex for up to 19 years. menstrual cycles. “

Limitations of the study included the fact that not all women tried to conceive; alcohol consumption has increased since the time of the study and the women in the study were on average thinner than women today; the study used self-reported data and women may underreport their alcohol consumption; and the influence of alcohol consumption by male partners has not been assessed.

She concluded: “Finally, the results of this study should not be interpreted to mean that while drinking alcohol prevents pregnancy. In other words, alcohol is not a method of birth control. Even if a woman drinks alcohol strongly, if she has unprotected sex, she can get pregnant. ”