I remember being pregnant and worried about everything I ate! Luckily, the amounts caffeine and lemongrass in the teas are very small and should NOT cause any problems. Nonetheless, this is your tea you're making at home. Find mint green tea and peach teas that don't include lemongrass. Don't worry too much about the caffeine, you'd need to drink about 200mg-300mg for it to be a problem. According to Starbucks, a 16 ounce Medicine Ball contains 16-25 mg of caffeine. Here's a link to the Cleveland Clinic's article about caffeine during pregnancy.