Many detox teas contain herbal laxatives (and can result in diarrhea or vomiting), which can cause the birth control to not be absorbed properly into someone's system. OB/GYN Dr. Nita Landry says this issue is not super common, but definitely possible.
ER physician Dr. Travis Stork says he is "concerned" with detox teas as they contain herbs and ingredients that oftentimes the user is not even aware of and could result in unforeseen side effects.
The Doctors also note that getting pregnant while in the midst of detox is not ideal. They stress that herbal tea is fine to drink while pregnant, but warn not to drink something if you are unsure what is exactly in it.