Intake of wine, beer and spirits and waiting time to pregnancy

Mette Juhl1,5, Jørn Olsen2, Anne-Marie Nybo Andersen3 and Morten Grønbæk4

1 Danish Epidemiology Science Centre at the Department of Epidemiology Research, Statens Serum Institut, 5 Artillerivej,DK-2300 Copenhagen S, 2 Danish Epidemiology Science Centre at the Department of Epidemiology and Social Medicine, 6 Vennelyst Boulevard, DK-8000 Aarhus C, 3 Department of Social Medicine, Institute of Public Health, University of Copenhagen, 3 Blegdamsvej, DK-2200 Copenhagen N and 4 Centre for Alcohol Research, National Institute of Public Health, 25 Svanemøllevej, DK-2100 Copenhagen Ø, Denmark

5 To whom correspondence should be addressed. e-mail: mju{at}ssi.dk


    Abstract
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
BACKGROUND: A high intake of alcohol may prolong waiting time to pregnancy, whereas a moderate intake may have no or perhaps even a positive effect on fecundity. In previous studies on fecundity, different types of beverages have not been taken into consideration, although moderate wine drinkers appear to have fewer strokes, lung and digestive tract cancers, and overall mortality than both abstainers and moderate drinkers of beer or spirits. We examined the association between different types of alcoholic beverages and waiting time to pregnancy. METHODS: Self-reported data were used for 29 844 pregnant women, recruited to the Danish National Birth Cohort in 1997–2000. Main outcome measures were odds ratios for a prolonged waiting time to pregnancy according to consumption of wine, beer and spirits. RESULTS: All levels of wine intake compared with non-wine drinking or with consumption of beer or spirits had subfecundity odds ratios between 0.7 and 0.9. No association was seen regarding beer drinking, while the association with spirits was J-shaped. CONCLUSION: Our findings suggest that wine drinkers have slightly shorter waiting times to pregnancy than both non-wine drinkers and consumers of other alcoholic beverages. Whether this is an effect of wine itself or the characteristics of the wine drinker is not known.

Key words: alcohol/beverage preference/birth cohort/fecundity/time to pregnancy


    Introduction
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
Various studies have examined the possible association between alcohol consumption and fecundity, defined as the time it takes for a sexually active couple not using contraception to obtain pregnancy. A large European multicentre study found a prolonged waiting time to pregnancy in women with a high intake of alcohol (more than 14 drinks per week) (Olsen et al., 1997Go). Some studies have suggested a negative impact on fecundity even at low levels of alcohol (Grodstein et al., 1994Go; Hakim et al., 1998Go; Jensen et al., 1998Go). Others have not found any association between moderate alcohol intake and waiting time to pregnancy (Olsen et al., 1983Go; Joesoef, 1993Go; Florack et al., 1994Go; Zaadstra et al., 1994Go; Curtis, 1997Go). In our recent study, we found that moderate drinkers had slightly shorter waiting times than abstainers (Juhl et al., 2002Go).

For public health matters it is desirable to know whether these findings are related to alcohol, the type of drink or to characteristics of the drinker. To our knowledge, no infertility studies have had the power or data to examine the effect of specific types of alcohol intake, or the data to adjust for confounding related to lifestyle.

It has been suggested that moderate wine drinkers are at lower risk of lung cancer (Prescott et al., 1999Go), digestive tract cancer (Grønbæk et al., 1998Go), stroke (Truelsen et al., 1998Go) and overall mortality (Grønbæk et al., 1995Go) compared with both non-drinkers and moderate drinkers of beer and spirits. It is under discussion whether these associations are related to specific components in wine, such as antioxidants or similar substances (Tjønneland et al., 1999Go).

The aim of this study was to examine the relation between specific types of alcohol consumption and waiting time to pregnancy.


    Materials and methods
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
Study population
This study was carried out within the Danish National Birth Cohort, a nationwide study of pregnant women and their offspring. More details about the birth cohort study are presented elsewhere (Olsen et al., 2001Go). Pregnant women in Denmark were invited to the study and participated in a telephone interview around weeks 12–16 of gestation. Altogether, 39 612 women were interviewed from October 1, 1997, to March 15, 2000. Out of the 39 612 recruited pregnancies, 29 933 were planned (76%), and these were the basis of this study. We excluded 89 women because of endometriosis, ovarian cancer or cervical cancer. Thus, 29 844 cases were included in this study.

We estimate that ~35% of all pregnant women in Denmark participated in the cohort study, which corresponds to ~60% of those invited.

Measurement of exposure and potential confounders
All participants were asked the question: ‘How many ordinary beers/glasses of wine/glasses of spirits did you drink per week before you became pregnant?’ One bottle of Danish beer contains 11.6 g of alcohol, and 12 g is an approximate average for one glass of wine (one-sixth of a bottle) or serving (4 cl) of spirits. If the woman reported to drink one type of beverage, but not on a weekly basis, this was coded as half a unit per week.

We did not have data on smoking before pregnancy, but if the participants reported to have smoked at any time in the first trimester we considered them to be smokers during waiting time to pregnancy. The rest were categorized as non-smokers.

BMI was calculated on the basis of the women’s reporting of their height and weight before pregnancy.

In the interview, use of oral contraceptives was reported only for the period up to 4 months before pregnancy.

The social variable used was generated from data on occupational status as a hierarchical type of variable with six categories: leaders and highly educated, middle range educated, self-employed and office or welfare workers, skilled and unskilled workers, students, and unemployed.

Measurement of outcome
The outcome measure was waiting time to pregnancy based upon the following question: ‘How long time did you try to become pregnant before you succeeded?’ followed by fixed answering categories: 0–2 months, 3–5 months, 6–12 months and >12 months. The women were also asked whether the pregnancy was planned, partly planned or not planned. If the pregnancy was not planned they were not asked about waiting time to pregnancy.

Statistical analysis
The association between wine, beer and spirit consumption and waiting time to pregnancy was estimated for a waiting time >12 months by means of logistic regression. Since estimates were similar at different cut-off levels, we combined the results using a discrete time survival method, according to the method of Kalbfleisch and Prentice (1980)Go. We used a logistic model to estimate the conditional probability of not getting pregnant within each waiting time interval given that the subject was not pregnant in the previous intervals. The intervals were 0–2 months, 3–5 months, 6–12 months and >12 months. All effect measures are given in subfecundity odds ratios, where a high odds ratio indicates a longer waiting time to pregnancy. Within each beverage type group we used the abstaining group as reference. In the model we included wine, beer and spirits consumption, potential confounders such as age, parity, smoking, thinness (BMI <18.5 kg/m2), obesity (BMI >30 kg/m2), pelvic inflammatory diseases, occupational status and a categorical variable to indicate the waiting time interval.

In addition, the discrete time survival analysis was replicated including the partly planned pregnancies. Analyses were also made with the use of preference groups (wine, beer, spirits, mixed and abstainers) and drinking pattern (only wine, wine and beer, wine and spirits, beer and spirits, and wine, beer and spirits) as explanatory variables. Stratified analysis was made on possible confounders. Since our data on the use of oral contraceptives were restricted to the last 4 months before pregnancy, this variable could not be used as adjustment variable. We examined a possible correlation between use of oral contraceptives and drinking habits in women with the shortest waiting time interval (0–2 months).

Analyses were carried out using SPSS 10.0 software.


    Results
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
Half of the women became pregnant within the first 2 months of trying, while 15% waited >12 months (Table I). In general, the women consumed more wine than beer in the planning period, and very little spirits. Almost 80% had a moderate intake of wine, between 0.5 and 7 glasses per week, whereas about half of the women consumed the same amount of beer.


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Table I. Characteristics of the 29 844 women with a planned pregnancy included in the study
 
Wine drinkers were more often pluripara and more often non-smokers than women who had some intake of beer or spirits (Table II). BMI was not associated with beverage preference. More abdominal or pelvic inflammatory diseases were reported in the high alcohol consumption groups, irrespective of the preferred type of beverage. A higher proportion of women with a waiting time >12 months was seen among those with the highest alcohol intake. In women who waited <=2 months to become pregnant, use of oral contraceptives was not associated with drinking habits. Only among women who reported no spirits consumption was there an over-representation of women not using oral contraception (data not shown).


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Table II. Distribution of potential confounders according to wine, beer, spirits and total alcohol consumption (planned pregnancies only)
 
Tables III and IV show the association between intake of wine, beer and spirits and waiting time to pregnancy, first, by using a waiting time >12 months as an indicator of subfecundity (Table III), and secondly, by using the entire distribution of waiting time in the analysis (Table IV). Wine drinkers experienced significantly shorter waiting times compared with those who reported no wine intake. With regard to beer consumption, no association was seen with waiting time to pregnancy. For spirits we found a J-shaped relation; shorter waiting times in the moderate intake group and longer for those with the higher reported intake. In general, women who reported no alcohol intake in the three beverage groups had longer waiting times than women who reported some intake. Age and parity were the adjustment variables that most changed the crude odds ratios. Including women with partly planned pregnancies in the analysis did not alter the estimates. Stratification on smoking showed modestly lowered odds ratios of wine drinking among smokers.


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Table III. Odds ratios for a waiting time to pregnancy >12 months according to weekly intake of wine, beer and spirits (planned pregnancies only)
 

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Table IV. Odds ratios for an increased waiting time to pregnancy (per increment of the waiting time categories in Table I) according to weekly intake of wine, beer and spirits (planned pregnancies only)
 
When we divided the participants into exclusive preference groups (beer, wine, spirits, mixed and abstainers), wine preferrers experienced the shortest waiting times (data not shown).

When we grouped the women according to their drinking patterns, we found that women who drank only beer or only spirits waited longer to become pregnant than all other combinations (only wine, wine and beer, wine and spirits, beer and spirits, and wine, beer and spirits) (data not shown). Women who drank all three types of alcohol had the shortest waiting times to pregnancy.

Women who had suffered from any kind of abdominal or pelvic inflammatory diseases (others than the already excluded, i.e. endometriosis, ovarian cancer and cervical cancer) waited longer to become pregnant than those who had not. No significant interaction was seen between type of alcoholic beverage and pelvic diseases (data not shown).


    Discussion
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
Wine drinkers had a shorter waiting time to pregnancy than non-wine drinkers. No association was seen for beer drinking, while the association with spirits was J-shaped.

The estimates for spirits consumption should be viewed with caution, since these groups included few pregnancies, especially the highest group with an intake of more than seven drinks per week (27 women).

Our study excluded infertile couples; therefore, proper fecundity effect measures cannot be estimated. Consequently, the rationale behind the estimates we present is that alcohol exposure may prolong waiting time rather than cause sterility. We expected alcohol to have such an effect, if it has any effect at all.

We have not been able to find published studies in fecundity research that distinguish between different types of beverages. Nevertheless, our results support earlier studies suggesting some beneficial health effects of wine drinking (Grønbæk et al., 1995Go; Grønbæk et al., 1998Go; Truelsen et al., 1998Go; Prescott et al, 1999Go). The wine drinking effect could be explained by residual confounding or uncontrolled confounding. If wine drinkers differ from others—if they, for example have fewer infections that cause sterility, have more sexual contacts, have more appropriate timing of intercourse, or have partners with better sperm quality—they would have shorter waiting times.

It has been shown that different drinking habits are strongly related to dietary habits. In a Danish study wine drinking was associated with an intake of healthier food (Tjønneland et al., 1999Go). Although we know very little about the association between dietary components and fecundity, these findings should be taken into account. A recent study showed that wine drinkers are at lower risk of becoming heavy or excessive drinkers than beer drinkers (Jensen et al., 2002Go), which supports the common opinion that beverage preference is associated with personality and lifestyle habits that can be difficult to adjust for fully.

Data on smoking before pregnancy were not available. We assumed that women who smoke during pregnancy also smoked before pregnancy, and that they were more likely to have been regular smokers and not just occasional smokers. The association with wine drinking may be underestimated if smoking is associated with larger waiting times, since fewer smokers were found among wine drinkers.

We found, as expected, that women who had had pelvic inflammatory diseases or abdominal diseases waited longer to become pregnant. However, the risk of subfecundity according to these diseases was not related to beverage preference. Although this finding argues against confounding by infection, it does not rule out residual confounding.

Use of oral contraceptives could be a confounding factor, but a correlation was only seen between non-users and women who reported no spirits consumption. Since use of oral contraceptives was reported only for a period up to 4 months before conception, we cannot adjust for this. Any confounding effect is expected to be small for waiting times of >6 months.

Socio-economic status is related to drinking habits, but does not seem to be associated with fecundity. A previous Danish study on 700 women showed no significant associations between subfecundity and family net income or employment status (Rachootin and Olsen, 1982Go). In our study, socio-economic status was measured by occupational status, and including this variable did not alter the estimates.

Self-reported data on alcohol intake are in general assumed to be under-reported. If there is a modest beneficial effect on fecundity associated with wine drinking, and under-reporting takes place, the effect may be underestimated.

A beneficial effect of wine drinking raises the question of whether such an association can be explained by a differential reporting pattern for the different types of alcoholic beverages. We have no indication to show that a possible under-reporting correlates with beverage preference. A previous report found no such association (Grønbæk and Heitmann, 1996Go).

The association between wine drinking and waiting time to pregnancy in this study was not very strong, and there was no clear dose–response pattern. We encourage others to check available data to see whether they find a similar beneficial effect of wine drinking.

In conclusion, our findings suggest that drinking wine may be associated with a modestly decreased risk of subfecundity. Subfecundity did not appear to be related to beer or spirits consumption.


    Acknowledgements
 
We thank Per Kragh Andersen at the Danish Epidemiology Science Centre for valuable comments on methodology in this study. The Danish National Research Foundation has established the Danish Epidemiology Science Centre that initiated and created the Danish National Birth Cohort. The cohort is furthermore a result of a major grant from this foundation. Additional support for the Danish National Birth Cohort is obtained from the Pharmacy Foundation, the Egmont Foundation, the March of Dimes Birth Defects Foundation, and the Augustinus Foundation. This particular study was supported by a grant from the Danish National Board of Health.


    References
 Top
 Abstract
 Introduction
 Materials and methods
 Results
 Discussion
 References
 
Curtis, K.M. (1997) Effects of cigarette smoking, caffeine consumption, and alcohol intake on fecundability. Am. J. Epidemiol., 146, 32–41.[Abstract]

Florack, E.I., Zielhuis, G.A. and Rolland, R. (1994) Cigarette smoking, alcohol consumption, and caffeine intake and fecundability. Prev. Med., 23, 175–180.[CrossRef][ISI][Medline]

Grodstein, F., Goldman, M.B. and Cramer, D.W. (1994) Infertility in women and moderate alcohol use [see comments]. Am. J. Public Health, 84, 1429–1432.[Abstract]

Grønbæk, M. and Heitmann, B.L. (1996) Validity of self-reported intakes of wine, beer and spirits in population studies. Eur. J. Clin. Nutr., 50, 487–490.[ISI][Medline]

Grønbæk, M., Deis, A., Sørensen, T.I., Becker, U., Schnohr, P. and Jensen, G. (1995) Mortality associated with moderate intakes of wine, beer, or spirits. BMJ, 310, 1165–1169.[Abstract/Free Full Text]

Grønbæk, M., Becker, U., Johansen, D., Tønnesen, H., Jensen, G. and Sørensen, T.I. (1998) Population based cohort study of the association between alcohol intake and cancer of the upper digestive tract. BMJ, 317, 844–847.[Abstract/Free Full Text]

Hakim, R.B., Gray, R.H. and Zacur, H. (1998) Alcohol and caffeine consumption and decreased fertility [published erratum appears in Fertil. Steril. 1999, 71, 974]. Fertil. Steril., 70, 632–637.[CrossRef][ISI][Medline]

Jensen, M.K., Andersen, A.T., Sørensen, T.I., Becker, U., Thorsen, T. and Grønbæk, M. (2002) Alcoholic beverage preference and risk of becoming a heavy drinker. Epidemiology, 13, 127–132.[CrossRef][ISI][Medline]

Jensen, T.K., Hjøllund, N.H., Henriksen, T.B., Scheike, T., Kolstad, H., Giwercman, A., Ernst, E., Bonde, J.P., Skakkebaek, N.E. and Olsen, J. (1998) Does moderate alcohol consumption affect fertility? Follow up study among couples planning first pregnancy [see comments]. BMJ, 317, 505–510.[Abstract/Free Full Text]

Joesoef, M.R. (1993) Fertility and use of cigarette, alcohol, marijuana, and cocaine. Ann. Epidemiol., 3, 592–594.[Medline]

Juhl, M., Nyboe Andersen, A.M., Grønbæk, M. and Olsen, J. (2002) Moderate alcohol consumption and waiting time to pregnancy. Hum. Reprod., 16, 2705–2709.[CrossRef][ISI]

Kalbfleisch, J.D. and Prentice, R.L. (1980) The Statistical Analysis of Failure Time Data. John Wiley and Sons, pp. 37–38.

Olsen, J., Rachootin, P., Schiøtt, A.V. and Damsboe, N. (1983) Tobacco use, alcohol consumption and infertility. Int. J. Epidemiol., 12, 179–184.[Abstract]

Olsen, J., Bolumar, F., Bisanti, L. and the European Study Group on Infertility and Subfecunity (1997) Does moderate alcohol intake reduce fecundability? Alcohol Clin. Exp. Res., 21, 206–212.[ISI][Medline]

Olsen, J., Melbye, M., Olsen, S.F., Sørensen, T.I., Aaby, P., Andersen, A.M., Taxbøl, D., Hansen, K.D., Juhl, M., Schow, T.B. et al. (2001) The Danish National Birth Cohort – its background, structure and aim. Scand. J. Public Health, 29, 300–307.[CrossRef][ISI][Medline]

Prescott, E., Grønbæk, M., Becker, U. and Sørensen, T.I. (1999) Alcohol intake and the risk of lung cancer: influence of type of alcoholic beverage. Am. J. Epidemiol., 149, 463–470.[Abstract]

Rachootin, P. and Olsen, J. (1982) Prevalence and socio-economic correlates of subfecundity and spontaneous abortion in Denmark. Int. J. Epidemiol., 11, 245–249.[Abstract]

Tjønneland, A., Grønbæk, M., Stripp, C. and Overvad, K. (1999) Wine intake and diet in a random sample of 48763 Danish men and women. Am. J. Clin. Nutr., 69, 49–54.[Abstract/Free Full Text]

Truelsen, T., Grønbæk, M., Schnohr, P. and Boysen, G. (1998) Intake of beer, wine, and spirits and risk of stroke: the copenhagen city heart study. Stroke, 29, 2467–2472.[Abstract/Free Full Text]

Zaadstra, B.M., Looman, C.W., te Velde, E.R., Habbema, J.D. and Karbaat, J. (1994) Moderate drinking: no impact on female fecundity. Fertil. Steril., 62, 948–954.[ISI][Medline]

Submitted on February 3, 2003; resubmitted on May 1, 2003; accepted on May 28, 2003.