Suddenly Broke Out In Hives I'm 12 Weeks Pregnant And Suddenly Broke Out With TONS Of Hives All Over My Belly!!!?

I'm 12 weeks pregnant and suddenly broke out with TONS of hives all over my belly!!!? - suddenly broke out in hives

At first it was 24 hours, and only very bad for four hours. I can think of nothing I have caused an allergic reaction to this issue would have thought, and the cortisone cream does not help, please help!