CYP1A2 and Miscarriage: Interestingly, epidemiologic research shows that fast caffeine metabolizers (higher CYP1A2 activity) are at greater risk of miscarriage when consuming caffeine, compared to slow metabolizers.[18] Specifically, women with high CYP1A2 activity face more than double the odds of miscarriage with moderate caffeine consumption compared to those with low activity (slower metabolism), who do not experience a significant increase in risk.[18] These data suggest that caffeine’s deleterious effects may hinge on its metabolic byproducts or the rate of its clearance.