Caffeine and Pregnancy
Numerous studies have been conducted to determine the effects of caffeine intake on fertility in women. One small study in 1988 suggested that caffeine equivalent to the amount consumed in 1 to 2 cups of coffee daily might decrease female fertility. However, the researchers acknowledged that delayed conception could be due to other factors they did not consider, such as exercise, stress, or other dietary habits. Since then, larger, well-designed studies have failed to support the 1988 findings.
In 1990, researchers at the Centers for Disease Control and Prevention (CDC) and Harvard University examined the association between the length of time to conceive and consumption of caffeinated beverages. The study involved more than 2,800 women who had recently given birth and 1,800 women with the medical diagnosis of primary infertility. Each group was interviewed concerning caffeine consumption, medical history, and lifestyle habits. The researchers found that caffeine consumption had little or no effect on the reported time to conceive in those women who had given birth. Caffeine consumption also was not a risk factor for infertility.
Supporting those findings, a 1991 study of 11,000 Danish women examined the relationship among number of months to conceive, cigarette smoking, and coffee and tea consumption. Although smokers who consumed eight or more cups of coffee per day experienced delayed conception, nonsmokers did not, regardless of caffeine consumption.
A study of 210 women, published in the American Journal of Public Health in 1998, examined the differences in fertility associated with consumption of different caffeinated beverages. This study, prompted by an inconsistency in previously reported findings, did not find a significant association between total caffeine consumption and reduced fertility. In fact, the researchers found that women who drank more than one-half cup of tea per day had a significant increase in fertility. This was particularly true with caffeine consumption in the early stages of a woman's attempt at conception. The caffeinated tea and fertility correlation was supported by a 1994 study; however, those women had significantly higher consumption levels.
OTIS reviewed the studies examining caffeine effects on fertility and concluded that, "Low to moderate caffeine consumption (less than 300 mg/day) does not seem to reduce a woman's chance of becoming pregnant."