The effects of drinking tea on the fetus: Caffeine in tea. Tea contains caffeine. This is a well-known fact. According to research, drinking tea can sometimes have negative effects on pregnant women and their fetuses. Caffeine can speed up the heartbeat of the fetus and can also affect the gastrointestinal tract and brain of pregnant women. Therefore, you should pay attention to your caffeine intake when drinking tea. If pregnant women drink tea too frequently,