Cersei's Child Will Kill Her

HBO

Assuming that Cersei wasn't lying to Tyrion and Jamie about her pregnancy, some theorists believe that she will die in childbirth. According to Maggie the Frog's prophecy, Cersei would have three children with blond hair and all would die before her.

So far, this has proven to be true. If the prophecy continues to play out, some believe that she will not live to have her fourth child, but will instead die during childbirth. This would also be slightly poetic, as it would mean that Jamie indirectly killed her, and their forbidden love would prove to be fatal.