קפאין ופוריות

לקפאין נמצא קשר שלילי חלש עם אי-פריון. ולכן יש מומחים שממציעים לפחות להפחית בכמות השתיה של משקות המכילים קפאין עבור אלו שמנסות להרות. תראי למשל: Am J Epidemiol 1997 Feb 15;145(4):324-34 Caffeine intake and delayed conception: a European multicenter study on infertility and subfecundity. European Study Group on Infertility Subfecundity. Bolumar F, Olsen J, Rebagliato M, Bisanti L. Department of Public Health, Alicante University, Spain. The effects of caffeine consumption on delayed conception were evaluated in a European multicenter study on risk factors of infertility. Information was collected retrospectively on time of unprotected intercourse for the first pregnancy and the most recent waiting time episode in a randomly selected sample of 3,187 women aged 25-44 years from five European countries (Denmark, Germany, Italy, Poland, and Spain) between August 1991 and February 1993. The consumption of caffeinated beverages at the beginning of the waiting time was used to estimate daily caffeine intake, which was categorized as 0-100, 101-300, 301-500, and > or = 501 mg. Risk of subfecundity (> or = 9.5 months) and the fecundability ratio, respectively, were assessed by logistic regression and Cox proportional hazard analyses, adjusting for age, parity, smoking, alcohol consumption, frequency of intercourse, educational level, working status, use of oral contraceptives, and country. A significantly increased odds ratio (OR) of 1.45 (95% confidence interval (CI) 1.03-2.04) for subfecundity in the first pregnancy was observed for women drinking more than 500 mg of caffeine per day, the effect being relatively stronger in smokers (OR = 1.56, 95% CI 0.92-2.63) than in nonsmokers (OR = 1.38, 95% CI 0.85-2.23). Women in the highest level of consumption had an increase in the time leading to the first pregnancy of 11% (hazard ratio = 0.90, 95% CI 0.78-1.03). These associations were observed consistently in all countries as well as for the most recent waiting time episode. The authors conclude that high levels of caffeine intake may delay conception among fertile women. Am J Epidemiol 1995 Dec 15;142(12):1322-9 Effects of caffeine consumption on delayed conception. Stanton CK, Gray RH. Department of Population Dynamics, Johns Hopkins University, School of Hygiene and Public Health, Baltimore, MD 21205, USA. The authors examined the effects of caffeine consumption on waiting time to conception in the Reproductive Health Study, a retrospective study of 1,430 non-contracepting, parous women interviewed between July 1989 and June 1990 at Fishkill, New York, and Burlington, Vermont. Information was obtained on 2,501 pregnancies since 1980. Women's reported consumption of caffeinated beverages during the first month of pregnancy was used to estimate daily caffeine intake, which was categorized as none, 1-150, 151-300, and > or = 301 mg. Information on delayed conception was analyzed as a dichotomous variable (ױ or = 12 months delay vs. > 12 months delay), and the per cycle probability of conception (fecundability) was estimated using waiting time to conception as a continuous variable. Odds ratios of delayed conception and fecundability ratios adjusted for age, parity, smoking, last contraceptive used, infertility history, and race, were estimated by logistic regression and Cox proportional hazard models, respectively. Women who did not smoke and who consumed no caffeine were used as a reference group. The adjusted odds ratio of delayed conception for more than one year was not increased among women who consumed or = 301 mg of caffeine daily. Although smoking per se was associated with a significant increased risk of delayed conception (OR = 1.77, 95% CI 1.33-2.37), no effect of high caffeine consumption was observed among women who smoked. Fecundability was reduced among nonsmokers who consumed more than 300 mg caffeine daily (fecundability ratio = 0.74, 95% CI 0.59-0.92). Smoking reduced the fecundability ratio, but the authors observed no effect of caffeine consumption on fecundability among women who smoked. Other studies provide biologic plausibility for these findings. The authors conclude that high levels of caffeine consumption may result in delayed conception among women who do not smoke cigarettes. Effects of cigarette smoking, caffeine consumption, and alcohol intake on fecundability. Am J Epidemiol 1997 Jul 1;146(1):32-41 Curtis KM, Savitz DA, Arbuckle TE. Department of Epidemiology, School of Public Health, University of North Carolina, Chapel Hill, USA. Data from the Ontario Farm Family Health Study were analyzed to determine whether smoking, caffeine, or alcohol use among men and women affect fecundability (the monthly probability of conception). In this retrospective cohort study of farm couples in Ontario, Canada, the farm operator, husband, and wife completed questionnaires during 1991-1992, yielding information on 2,607 planned pregnancies that had occurred over the previous 30 years. Fecundability ratios were calculated using an analog of the Cox proportional hazards model. Cigarette smoking among women and men was associated with decreased fecundability (fecundability ratio = 0.90, 95% confidence interval (CI) 0.82-0.98 and fecundability ratio = 0.88, 95% CI 0.81-0.95, respectively). Caffeine consumption of 100 mg or less versus more than 100 mg in women and men was not associated with fecundability (fecundability ratio = 0.98, 95% CI 0.91-1.07 and fecundability ratio = 1.05, 95% CI 0.97-1.14, respectively). Decreases were observed among women who were coffee drinkers (fecundability ratio = 0.92, 95% CI 0.84-1.00) and men who were heavy tea drinkers (fecundability ratio = 0.85, 95% CI 0.69-1.05), regardless of caffeine content. Alcohol use among women and men was not associated with fecundability. These data are consistent with previous studies of the adverse effect of tobacco on fecundability in female smokers and suggest an effect of smoking among males. Continued evaluation of coffee and tea is warranted to address constituents other than caffeine.