EFFECTS OF CAFFEINE CONSUMPTION ON DELAYED CONCEPTION

The authors examined the effects of caffeine consumption on waiting ti me to conception in the Reproductive Health Study, a retrospective stu dy of 1,430 non-contracepting, parous women interviewed between July 1 989 and June 1990 at Fishkill, New York, and Burlington, Vermont. Info rmation was obtained on 2,501 pregnancies since 1980, Women's reported consumption of caffeinated beverages during the first month of pregna ncy was used to estimate daily caffeine intake, which was categorized as none, 1-150, 151-300, and greater than or equal to 301 mg, Informat ion on delayed conception was analyzed as a dichotomous variable (less than or equal to 12 months delay vs, >12 months delay), and tile per cycle probability of conception (fecundability) was estimated using wa iting time to conception as a continuous variable. Odds ratios of dela yed conception and fecundability ratios adjusted for age, parity, smok ing, last contraceptive used, infertility history, and race, were esti mated by logistic regression and Cox proportional hazard models, respe ctively. Women who did not smoke and who consumed no caffeine were use d as a reference group. The adjusted odds ratio of delayed conception for more than one year was not increased among women who consumed less than or equal to 300 mg of caffeine daily, However, the odds ratio (O R) was 2.65 (95% confidence interval (CI) 1.38-5.07) among nonsmokers who consumed greater than or equal to 301 mg of caffeine daily. Althou gh 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 ca ffeine consumption was observed among women who smoked. Fecundability was reduced among nonsmokers who consumed more than 300 mg caffeine da ily (fecundability ratio = 0.74, 95% CI 0.59-0.92). Smoking reduced th e fecundability ratio, but the authors observed no effect of caffeine consumption on fecundability among women who smoked. Other studies pro vide biologic plausibility for these findings, The authors conclude th at high levels of caffeine consumption may result in delayed conceptio n among women who do not smoke cigarettes.