RELATION OF FEMALE INFERTILITY TO CONSUMPTION OF CAFFEINATED BEVERAGES

Several studies have reported an association between caffeine intake a nd delay to conception. To study this relation further, the authors ex amined caffeine use in 1,050 women with primary infertility and 3,833 women who had recently given birth during the period 1981-1983 in the United States and Canada. The cases were separated by the cause of the ir infertility: ovulatory factor, tubal disease, cervical factor, endo metriosis, or idiopathic infertility. The relative risks of each type of infertility associated with caffeine were calculated using separate logistic regression models and controlling for relevant confounding f actors, such as age, center, cigarette smoking, lifetime number of sex ual partners, alcohol consumption, contraception, body mass index, and exercise. A significant increase in the risk of infertility due to tu bal disease or endometriosis was observed for the upper levels of caff eine intake, indicating a threshold effect. For tubal infertility, a r elative risk of 1.5 (95% confidence interval (CI) 1.1-2.0) was found i n women who consumed more than 7 g of caffeine per month as compared w ith those who consumed 3 g or less per month. For endometriosis, the r elative risk was 1.9 (95% CI 1.2-2.9) in women who consumed 5.1-7 g/mo nth and 1.6 (95% CI 1.1-2.4) in those with an intake of more than 7 g/ month. These data suggest that caffeine deserves further study with re gard to its effects on the female reproductive system.