Drinking alcohol is linked to reduced chances of pregnancy

A study that examined the associations between drinking alcohol and the chances of becoming pregnant suggests that women who want to conceive should avoid heavy drinking. In the second half of menstrual cycle even moderate drinking is linked to reduced chances of pregnancy.
The study, that appears in the journal Human Reproduction, investigated alcohol intake and fecundability, which is defined as the probability of conceiving during a single menstrual cycle. It is the first study to look at this according to the difference phases of women’s menstrual cycles.
Researchers led by Dr Kira Taylor, associate professor of epidemiology and population health at the University of Louisville School of Public Health and Information Sciences (Kentucky, USA), analysed data from the Mount Sinai Study of Women Office Workers. Women aged 19-41 years were recruited between 1990 and 1994 and followed for a maximum of 19 menstrual cycles. The women completed daily diaries reporting how much alcohol they drank and what type, and they provided urine samples on the first and second day of each menstrual cycle in order to check for pregnancy.
Heavy drinking was defined as more than six alcoholic drinks a week, moderate drinking was three to six drinks a week, and binge drinking was defined as four or more drinks on a single day. Each drink consisted of a third of a litre of beer (355 millilitres), a medium glass of wine (148 millilitres), or just under a double shot of spirits (44 millilitres). The researchers collected 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 current study.
Compared to non-drinkers both moderate and heavy drinking during the luteal phase was linked to a reduction in the odds of conceiving by about 44%. Heavy drinking during the ovulatory part of the cycle was also associated with significant 61% reduced odds of becoming pregnant. However, the researchers stress these are all estimates and should be treated with caution.
“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,” said Dr Taylor. “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.”
Each extra day of binge drinking was associated with an approximate 19% reduction in the odds of conceiving during the luteal phase and a 41% reduction during the ovulatory phase. The researchers found no difference in their results between different types of drinks.
The results suggest an inverse association between alcohol and fecundability, and support the relevance of menstrual cycle phases in this link. More specifically, moderate to heavy drinking during the luteal phase, and heavy drinking in the ovulatory window, could disturb the delicate sequence of hormonal events, affecting chances of a successful conception.
Source: Mohammad Yaser Anwar, Michele Marcus, Kira C Taylor. The association between alcohol intake and fecundability during menstrual cycle phases. Human Reproduction, 2021; .