The association between alcohol intake and fecundability during menstrual cycle phases.

Study question Is increased alcohol intake in different phases of the menstrual cycle associated with fecundability in women? Summary answer Heavy intake (>6 drinks/week) of alcoholic beverages in the luteal phase and ovulatory subphase was associated with reduced odds of conception; moderate intake (3-6 drinks/week) during the luteal phase was also associated with reduced fecundability. What is known already Despite strong indications for increased risk of infertility among drinking women with intention to conceive, inconsistencies in previous results point to possible residual confounding, and have not thoroughly investigated timing of drinking and other drinking patterns during the menstrual cycle. Study design, size, duration Participants in The Mount Sinai Study of Women Office Workers (MSSWOW), a prospective cohort study of fertility, were recruited and followed between 1990 and 1994, and completed daily diaries reporting their alcohol intake (type and number of drinks) for a maximum of 19 months of follow-up (N = 413). Participants/materials, setting, methods Participants were between 19 and 41 years of age. After completion of baseline surveys, they were asked to record their alcoholic beverage intake as number of drinks of beer, wine, and liquor per day, in addition to other exposures such as caffeine and smoking. Furthermore, they submitted urine samples each month to assess pregnancy. Menstrual cycle phases were calculated using the Knaus-Ognio approach. Discrete survival analysis methods were employed to estimate the association between categories of alcohol intake in each phase of menstrual cycle and fecundability. Main results and the role of chance In the luteal phase, both moderate drinking (3-6 drinks/week, Fecundability Odds Ratio (FOR)=0.56, CI: 0.31, 0.98) and heavy drinking (>6 drinks/week, FOR = 0.51, CI: 0.29, 0.89) were associated with a reduction in fecundability, compared to non-drinkers. For the follicular phase, heavy drinking in the ovulatory sub-phase (FOR = 0.39, CI: 0.19, 0.72) was similarly associated with reduced fecundability, compared to non-drinkers. For the pre-ovulatory sub-phase, heavy drinking (>6 drinks/week, FOR = 0.54, CI: 0.29, 0.97) was associated with reduction in fecundability, but this association was inconsistent when subjected to sensitivity tests. Each extra day of binge drinking was associated with 19% (FOR = 0.81, CI: 0.63, 0.98), and 41% (FOR = 0.59, CI: 0.33, 0.93) reduction in fecundability for the luteal phase and ovulatory sub-phase respectively, but no association was observed in the pre-ovulatory sub-phase. No meaningful differences in fecundability between beverages were observed in any menstrual phase. Limitations, reasons for caution Patterns of alcohol intake in this cohort suggest a lower average alcohol intake compared to more recent national averages for the same demographic group. Sample sizes were small for some subgroups, resulting in limited power to examine specific beverage types in different phases of the menstrual cycle, or to assess interaction. In addition, the influence of male partner alcohol intake was not assessed, the data relied on self-report, and residual confounding (e.g. unmeasured behaviors correlated with alcohol intake) is a possibility. Wider implications of the findings 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. Study funding/competing interest(s) Authors declare no conflict of interest. This work was supported by the National Institutes of Health grant, R01-HD24618. Trial registration number N/A.