Alcohol Intake and Timing Negatively Affects Getting Pregnant

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Alcohol intake and timing negatively affects getting pregnant

The association between alcohol intake and fecundability during menstrual cycle phases

doi.org/10.1093/humrep/deab121

Background

Fecundability is defined as the probability of conception in a single menstrual cycle.

Studies on the effect of alcohol intake on fecundability have had inconsistent results so far possibly due to poor methodology.

Selection bias, change in drinking behaviour with age, potential underestimation, lifestyle and other confounding factors all make alcohol-fecundability studies challenging.

In addition, no prior studies assessed the timing of alcohol intake, which could have varying degrees of impact on ovulation, conception or implantation.

Aim

To evaluate whether alcohol intake in premenopausal women is associated with the probability of conception, during any specific phase of the menstrual cycle (pre-ovulatory, ovulatory, and luteal) and if binge drinking, types of alcoholic beverages, smoking or caffeine changed this association.

Methodology

Women from the Mount Sinai Study of Women Office Workers (MSSWOW) were invited to participate in a follow-up study which involved a baseline interview, daily diaries and urine sample collection.

Women with a prior hysterectomy, short menstrual cycles (<22 days), not actively trying to conceive, diagnosed with infertility, undergoing fertility treatment, did not provide urine samples or alcohol intake information and had partners with vasectomies, were automatically excluded from the study to minimise potential bias.

In total of 413 women satisfied the inclusion exclusion criteria and were required to complete daily diaries and collect urine samples at least 2 days each menstrual cycle (cycle day 1 and 2). 

Women were grouped according to mean alcohol intake per week; 

GroupSize
Non-drinkers46
Light drinkers (1-2 drinks)182
Medium drinkers (3-6 drinks)104
Heavy drinkers (> 6 drinks)81

Menstrual cycle characteristics, frequency and time of intercourse, use of birth control methods, caffeine intake, smoking, stress level, physical exercise and intake of drinks containing alcohol (beer, wine or liquor) was recorded in the diaries.

Pregnancy was confirmed by hCG levels greater than 0.25ng/ml on 2 consecutive days, during a 4-day period beginning at the expected day or onset of menses.

A number of sensitivity analyses was then carried out on the final results to test the strength of any findings.

Results

Of the 413 women, almost one third (n=133) fell pregnant during the study period. Median follow-up time was 4 cycles with a reported median alcohol intake of 0.27 drinks/day or 1.9 drinks per week. The average daily alcohol intake did not change significantly during the menstrual phase / sub-phases.

Baseline characteristics of the women between all groups were comparable however initial results showed that women higher than average alcohol intake (> 6 drinks/week) were less likely to conceive during the study period compared to the non-drinking women (27% vs. 41%) and more likely to be smokers.

Advanced statistical analysis of alcohol intake and fecundability during the menstrual phases and sub-phases found that during the luteal phase, moderate and heavy drinking was associated with significantly reduced fecundability (FOR = 0.56 and 0.51 respectively), while in the ovulatory sub-phase and pre-ovulatory sub-phase only heavy drinking was significantly associated with reduced fecundability (FOR = 0.38 and 0.54).

Overall when analysing the entire cycle, only heavy drinking was significantly associated with reduced fecundability (FOR = 0.51).

Analysis of fecundability by beverage type and quantity was found to be imprecise due to the reduced sub-group sizes although some analysis did show that beer drinkers were more likely to be heavy drinkers and 3.5 times more likely to binge drink, compared to just 1.1 for wine and 1.2 for liquor drinkers vs. non-drinkers.

Interestingly further analysis showed that each extra day of binge drinking was associated with a 9% reduction in fecundability, while analysis for any associations between smoking, caffeine, stress level, exercise and BMI did not find any significant links.

Finally sensitivity analysis of the results using 3 different models (assumptions) showed negligibly meaningful variations to the strength of the results although overall, any drinking in the luteal phase was associated with reduced fecundability in a dose-dependent manner.

In general, the results demonstrate a clear inverse relationship between alcohol intake and fecundability, particularly during critical physiological intervals of the menstrual cycle, the luteal phase and ovulatory sub-phase.

SUMMARY: CAN ALCOHOL STOP YOU FROM GETTING PREGNANT

In this study the consumption of alcohol by women had a negative effect on the probability of getting pregnant per menstrual cycle, with heavy drinking (> 6 drinks/week) significantly reducing fecundability by 49%, plus a further 9% for each day of binge drinking.

Limitations

  1. Undersized study for various sub-analysis
  2. Lack of information on male partners
  3. Self-reporting of alcohol consumption

Funding

This study was supported by a National Institutes of Health grant.

Glossary

Confounding
A distortion that modifies the estimated measure of an association.

FOR
Fecundability Odds Ratio.

Luteal
Second half of the menstrual cycle, from ovulation to the start of menstruation.

Median
The middle number of a sorted data set.

Ovulatory phase
5 days preceding the luteal phase.

Pre-ovulatory sub-phase
The follicular phase.

Similar studies

Fan D, et al. (2017). Female alcohol consumption and fecundability: a systematic review and dose-response meta-analysis. https://doi.org/10.1038/s41598-017-14261-8

Mikkelsen E M, et al. (2016). Alcohol consumption and fecundability: prospective Danish cohort study. https://doi.org/10.1136/bmj.i4262

Patra J, et al. (2011). Dose-response relationship between alcohol consumption before and during pregnancy and the risks of low birthweight, preterm birth and small for gestational age (SGA)-a systematic review and meta-analyses. https://doi.org/10.1111/j.1471-0528.2011.03050.x


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