A study published in Human Reproduction looks at alcohol intake and fecundability during menstrual cycle phases.
Dr Sadie Boniface, Head of Research, Institute of Alcohol Studies and Visiting Researcher, King’s College London, said:
“The title of the press release reads that ‘women should avoid alcohol in second half of menstrual cycle’, but it then goes on to clarify this refers to those who are trying for a baby.
“The NHS already recommends that alcohol should be avoided for women planning to become pregnant (https://www.nhs.uk/pregnancy/keeping-well/drinking-alcohol-while-pregnant/). This existing advice applies to throughout the menstrual cycle for those trying to conceive, not just in the second half of the menstrual cycle, the exact timing of which can be difficult to predict anyway.
“They have adjusted for confounders and this was a longitudinal study. However it’s still hard to say whether the study’s findings about the second half of the menstrual cycle indicate a causal link. This is a relatively small study.
“The research also defined heavy drinking at a relatively low level of six or more drinks a week. The fact that they found an association at this level with reduced chances of pregnancy highlights the best option is to follow the existing NHS advice to avoid alcohol altogether when trying for a baby.
“Most people are aware that alcohol should be avoided during pregnancy. The UK drinking guidelines were updated in 2016, however they weren’t well communicated to the public or to health professionals such as midwives (https://www.ias.org.uk/wp-content/uploads/2020/06/rp37092019.pdf). The forthcoming consultation on alcohol labelling is an opportunity to introduce independent health information on alcohol products so that consumers can make fully informed decisions about their drinking.”
Dr Gill Lockwood, Medical Director at Care Fertility Tamworth, said:
“I have significant concerns about this study and its conclusions. It is very old (data gathered between 1990 and 1994!). It’s not clear to me why these results have been for 25 years.
“The age range of 19-41 and the fact that only 25% were even trying to conceive could mean the conclusions might be misleading or might not apply generally.
“To suggest that couples have a 25% chance ‘each month’ of conceiving may be true up to the early 30s but is not true for older ages or for couples who have been trying longer than 6 months. A 40 year old, with normal fertility, has a 10% chance of getting pregnant each month and a 40% chance of an early miscarriage. If people think ‘you have a 1 in 4 chance each month’ that may cause distress and unnecessary delays in seeking help.
“America has had a strange relationship with alcohol ever since Prohibition, but to claim that 1 bottle of wine a week is ‘heavy’ drinking is not really accurate. This is, after all, a country which locks up pregnant women if they are caught drinking. Alcohol consumption (especially if self-reported) correlates with age, education, socio-economic group, health, weight, smoking, marital status and male factors.
“There are excellent scientific reasons, which we know about from other research, to expect that alcohol consumption could correlate (inversely) with fecundity as ovulation is an inflammatory process and that is why taking high doses of NSAIDs such as Ibuprofen around the time of ovulation to deal with Mittelschmerz (ovulation pain) has been shown to impair egg release.
“An excellent Danish study demonstrated that there appeared to be a ‘dose-dependent’ link between alcohol consumption and miscarriage. The RCOG now says that there is no ‘safe’ level for drinking in pregnancy and so we already know from other research that it makes excellent sense for women trying to conceive to stop before they start ‘trying’. Cycle irregularity after stopping the pill or other hormonal contraceptive methods means that many women may not be aware straight away that they are pregnant and this study, despite its limitations, may support this view.”
Dr Ying Cheong, Professor of Reproductive Medicine, University of Southampton, said:
“Anwar and colleagues studied the link between alcohol intake at different times of the menstrual cycle and fertility in 413 women. They found that moderate and heavy alcohol drinkers had a much lower fertility in all phases of the menstrual cycle compared to non-alcohol drinkers. Whilst this study conveys an important health and lifestyle message to people who are trying to conceive, that is, to limit their alcohol consumption when attempting conception, the study suffers from several study flaws and bias which weakens the validity of the study.
“Not only was the dataset quite small for a significant number of subgroups included, the data was from a good 30 years ago, and hence the context is no longer current. The study was subjected to recollection bias as it was based on self-reporting, and there was no data on male partners.
“I think future lifestyle studies such as this must consider biological sampling, as not only would we then have a much richer source of biological data to collate to behaviour, we may also be able to capture biomarkers relevant in health and disease.”
Prof Tim Child, Group Medical Director, TFP Oxford Fertility, and Associate Professor in Reproductive Medicine, University of Oxford, said:
“The press release does summarise the study and some of the possible issues with it.
“The data were collected 30 years ago, the numbers enrolled and eligible were fairly small (417) and a minority were wanting to conceive. Lifestyle factors of the male partner were also not considered – perhaps partners of women who were heavy or binge drinkers were themselves less fertile and that’s the association?
“Whilst previous studies have been conflicting (many much larger than this one) it is reasonable to assume that heavy or binge drinking can reduce fertility, and that is the finding this study supports.
“The association with phase of the cycle is interesting and has biological plausibility, having a greater effect when heavy or binge drinking around or after ovulation. Therefore, women wishing to conceive can be reassured that low amounts of alcohol appear to not affect fertility but heavy or binge drinking is best avoided if they wish to maximise the chance of success.”
Dr Gareth Nye, Programme Lead for Medical Science and lecturer in anatomy and physiology at Chester Medical School, University of Chester, said:
“The association with drinking alcohol and pregnancy complications has long been established once a pregnancy is confirmed, however what is not clear, is how alcohol influences the conception process. With infertility becoming a rising issues globally, any new research into fertility and conception is highly sought after.
“In this study, researchers have utilised data from a study in the early 1990s, some 30 years ago and this brings with it certain issues with relevance to today’s culture, data acquisition and storage at the time.
“There are a number of places where the new research is unclear which may make the case less compelling, particularly with the wording of the press release:
“Crucially they conclude only a possible association with heavy drinking and reduced fertility and although important to note, this paper does not prove the fact.
“We would always advise limiting alcohol during the pregnancy period. Women who are struggling to conceive are also asked to limit alcohol intake as heavy consumption can impact on ovulation cycles. This paper unfortunately does not change any current advice and work would be needed in women now to understand the impact of alcohol on conception.
“Ultimately, it is advisable that women who are pregnant, or are struggling to get pregnant limit alcohol intake along with other lifestyle changes such as diet, exercise and caffeine intake and this paper does not change that message.”
Prof Joyce Harper, Head of the Reproductive Science and Society Group, UCL Institute for Women’s Health, UCL, said:
“There has been much contradictory advice for women about alcohol consumption and fertility. This important study of 413 women demonstrates that even moderate alcohol consumption can affect the chances of getting pregnant by 61% for heavy drinkers and 44% for moderate drinkers.
“There are limitations to the study, as not all women were trying to get pregnant, male partner alcohol consumption was not considered and 413 women is not a large sample size, but the study adds to the growing evidence of the importance of preconception health.
“One of the strengths of the paper is that they looked at pregnancy rates rather than any other indictor of fertility.
“The authors define heavy drinking as over six alcoholic drinks a week and moderate drinking as three to six drinks a week, with one drink being a medium glass of wine. Unfortunately drinking 1-2 drinks a night is commonplace, especially during the last year and many women may not realise that they would be classed as heavy drinkers. Reducing alcohol consumption for men and women who are trying to conceive is sensible advice as a growing number of studies have shown preconception lifestyle factors such as alcohol consumption can reduce fertility and have a long term effect on the health of the future child.”
Prof Allan Pacey, Professor of Andrology, University of Sheffield, said:
“This is a really nice epidemiological paper which investigates the relationship between alcohol intake in women across their menstrual cycle and to see whether this correlated with their chances of becoming pregnant. Like any epidemiological study this is correlation rather than causation, but the strength of this study is its prospective design.
“The results would seem to suggest there is a significant association between the chances of a woman becoming pregnant and heavy drinking during the middle to latter part of the menstrual cycle. This corresponds to the time when the egg is released from the ovary and also the time when the developing embryo is travelling down the Fallopian tube and implanting into the lining of the uterus.
“This study design is unable to establish why drinking alcohol during this time causes these effects and moreover, as the authors also conclude, it is possible that the effect they observe is being caused by other factors that they did not measure, but which are themselves correlated with the alcohol consumption of women in the study.
“For example, it is noteworthy that the study did not measure the alcohol consumption of the women’s partners and this could have an independent impact on the chances of pregnancy via a direct effect on sperm in some way.
“Overall I would conclude from this study that for couples who want to maximise their chances of achieving pregnancy it’s probably wise to reduce alcohol intake to less than three drinks per week and certainly avoid binge drinking.”
‘The association between alcohol intake and fecundability during menstrual cycle phases’ by Mohammad Yaser Anwar et al. was published in Human Reproduction at 00:05 UK time on Wednesday 9 June 2021.
Dr Sadie Boniface: “I work at the Institute of Alcohol Studies which receives funding from the Alliance House Foundation.”
Prof Tim Child: “Employee and Shareholder in TFP;
Person Responsible Oxford Fertility;
Member of HFEA Authority;
Honoraria for educational activities Ferring and Merck.”
Dr Ying Cheong: “I am the medical director of Complete Fertility.”
Dr Gareth Nye: “No conflicts.”
Prof Allan Pacey: “Chairman of the advisory committee of the UK National External Quality Assurance Schemes in Andrology, Editor in Chief of Human Fertility, Trustee of the Progress Educational Trust (Charity Number: 1139856) and Trustee of the British Fertility Society (Charity Number:1075661) (all unpaid).”
None others received.