Women who drink during luteal phase less likely to conceive

Women who drink alcohol during the second half of their menstrual cycle lower their chances of conception, a new study has found.

The luteal phase of a woman's menstrual cycle describes the period of time from ovulation through to the start of menstruation when hormones including progesterone and oestrogen are secreted by the ovary. These hormones maintain the thickness of the endometrial lining to prepare the uterus for the implantation of an embryo, and it is thought that alcohol could interfere with their secretion.

'This is the first study to examine the effect of alcohol on fecundability [the likelihood somebody will conceive in a given cycle] during specific phases of the menstrual cycle' said Dr Kira Taylor, one of the study's authors.

Previous studies investigating the effects of women's alcohol intake on their likelihood to conceive had suggested a negative relationship, but had yet to establish a statistical correlation that accounted for variables such as smoking, obesity, and age. Researchers at the University of Louisville, Kentucky, analysed data collected from 413 women who recorded their daily alcohol intake across 19 months between 1990 and 1994, specifying both the number and type of drink. An alcoholic drink was classed as 335 ml of beer (a bottle), 148 ml of wine (a medium glass) or 44 ml of spirits (a double shot).

Researchers assumed ovulation to have occurred 14 days before the start of menstruation, which was reported by participants in the study. Drinking three or more alcoholic beverages per week, which is classified as 'moderate drinking', during their luteal phase resulted in a 44 percent reduction in a woman's likelihood to conceive that cycle. Whereas if the woman had drunk six or more drinks in the week in which she was assumed to have ovulated, classed as 'heavy drinking', the likelihood of becoming pregnant that cycle dropped by 61 percent. Furthermore, each day of binge drinking which equates to drinking four or more alcoholic drinks during the luteal phases, led to a further 19 percent decrease in likelihood of conception that cycle. 

This study, published in the journal Human Reproduction, focused exclusively on women's drinking patterns and its effects on their fecundability without addressing the corresponding behaviour of their respective male partners. '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 direct effect on sperm in some way' said Professor Allan Pacey, professor of andrology at the University of Sheffield who was not involved in the research.

With as many as 12 percent of couples having trouble in conceiving, these findings could provide them with further guidance on how best to tailor their drinking habits to maximise the women's ability to conceive during each cycle. However, currently the mechanisms by which alcohol affects a women's menstrual cycle and ovulation have yet to be fully determined and warrant further quantitative research. 'Like any epidemiological study this is correlation rather than causation, but the strength of this study is its prospective design.' said Professor Pacey.