 [ Symptoms ] do multivitamins descrease the effectiveness of oral birth control pills [ Disease ] i remember i had this same questiosn when i was pregnant and unfortunately things like herbal teas are not often on the typical do no eat list for pregnant women that said i would definitely ask your ob about this although herbal teas are natural they are not regulated so you can never be sure what you are getting plus there is not much research to know for sure whether any specific ingredients are harmful i remember i pretty much avoided them here is some more information that may help <link>