Searching through the biomedical literature, I looked at four major categories of caffeine effects on the developing fetus. The first category, major birth defects, was easy to evaluate. Very high levels of caffeine have been shown to cause birth defects in animals (Nehlig & Debry 1994), but the levels at which these effects are seen are so high that they would not practically apply to even staunchly caffeine-addicted humans. To assess whether caffeine has these kinds of effects in humans, epidemiological studies (studies of populations of humans) must be used. In a systematic review of the epidemiological literature on cardiovascular malformations and oral clefts (Browne 2006), no evidence was found that caffeine alone was teratogenic for humans. [Caffeine has, however, been found to increase the risk of birth defects by other substances, such as tobacco and alcohol (Nehlig & Debry 1994)]. In a review of several animal studies and epidemiological studies exploring birth defects in general, Christian & Brent (2001) concluded that moderate caffeine use alone should not put fetuses at risk for birth defects. The outcome of epidemiological studies and the extremely high levels of caffeine needed to cause birth defects in animals is reassuring- moderate caffeine use should not lead to birth defects in humans.