Call your provider immediately if you think you have the flu. It's serious when you're pregnant — even to the point that you could be hospitalized. High fever in the first trimester can lead to birth defects in an unborn child, or even premature labor and delivery. Your provider may prescribe an antiviral medication like Tamiflu if they feel you have a clinical diagnosis of the flu, says Shirazian. That drug helps minimize symptoms and decreases the length of time you are symptomatic, which can help keep baby safe.