Any amount of alcohol consumption linked to lower pregnancy chances

Doctors suggest avoiding alcohol entirely during the second half of a menstrual cycle for women hoping to have a baby.

LOUISVILLE, Ky. — Women hoping to become pregnant in the near future should avoid alcohol altogether to give themselves the best chance of conceiving. That advice comes from a new study by researchers with the European Society of Reproduction and Embryology. Their findings reveal binge drinking or heavy alcohol use is the most detrimental to pregnancy odds. However, they add even moderate alcohol consumption during the second half of a menstrual cycle can reduce a woman’s chances of pregnancy.

Study authors set out to investigate the relationship between alcohol intake and fecundability, or the chances of conceiving during a single menstrual cycle. Plenty of earlier research projects have focused on alcohol and pregnancy, but this is the first such initiative to investigate the role of women’s menstrual cycles specifically.

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The team relied on data from the Mount Sinai Study of Women Office Workers during this investigation. That dataset featured a collection of 413 women between 19 and 41 years-old, originally recruited between 1990 and 1994. Scientists tracked the group for a maximum of 19 menstrual cycles. During that time, each woman also kept a diary of her daily drinking habits. Researchers collected urine samples on the first and second day of each menstrual cycle to check for pregnancy.

For this study, the team defined heavy drinking as having more than six alcoholic beverages per week. Moderate drinking fell into the three to six drink per week range and binge drinking included anyone consuming four or more drinks in a single day. Each “drink” consisted of either a third of a liter of beer (355 milliliters), a medium glass of wine (148 milliliters), or just below a double shot of liquor or spirits (44 milliliters). The team also accounted for additional health, demographic, and lifestyle factors, including birth control use, age, smoking habits, and each participant’s intention of becoming pregnant.

“We found that heavy drinking during any phase of the menstrual cycle was significantly associated with a reduced probability of conception compared to non-drinkers. This is important because some women who are trying to conceive might believe it is ‘safe’ to drink during certain parts of the menstrual cycle,” says research leader Dr. Kira Taylor, associate professor of epidemiology and population health at the University of Louisville School of Public Health and Information Sciences in a media release. “During the luteal phase, which is the last two weeks of the menstrual cycle before bleeding would start and when the process of implantation occurs, not only heavy drinking but also moderate drinking was significantly associated with a reduced probability of conception.”

“At the time of ovulation, usually around day 14 of the cycle, consuming a lot of alcohol – either heavy or binge drinking – was significantly associated with reduced chances of conception,” Dr. Taylor adds.

Abstinence is the best choice when it comes to pregnancy

In comparison to totally avoiding alcohol, the study reveals both moderate and heavy drinking during the luteal phase resulted in a 44-percent lower chance of conceiving. Heavy drinking during the ovulatory phase also lowered pregnancy odds by 61 percent.

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

“Our study only included a few hundred women and, while we believe the results strongly suggest that heavy and even moderate alcohol intake affects the ability to conceive, the exact percentages and numbers should be viewed as rough estimates,” she clarifies.

Binge drinking has a major impact on fertility

Researchers also discovered that each additional day of binge drinking leads to a 19-percent drop in conception odds during the luteal phase and a 41-percent reduction during the ovulatory phase. Importantly, study authors mention that the type of alcohol consumed appears to make no difference at all.

To be clear, these findings cannot confirm that alcohol causes lower pregnancy odds. What it can confirm is that there is an association between alcohol consumption and a reduced chance of pregnancy. From the perspective of biological mechanisms, researchers speculate this relationship may be due to alcohol’s effect on the processes involved in ovulation.

“Finally, the results in this study should not be construed to mean that drinking alcohol prevents pregnancy. In other words, alcohol is not birth control. Even if a woman drinks alcohol heavily, if she has unprotected intercourse, she can become pregnant,” Dr. Taylor concludes.

The study appears in the journal Human Reproduction.

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