Continuity mistake: When Bella is first seen pregnant, she is wearing grey pants, a blue shirt and navy jacket, Edward is wearing a brown shirt, and Carlisle is wearing a blue mock turtleneck. On what is supposed to be the next day (and after having seen them wearing different clothing), all three are wearing the same clothes again while in the library/makeshift hospital room. They are discussing a cracked rib that was causing Bella pain the day before. These scenes were obviously meant to be back-to-back, but were rearranged in editing.
Continuity mistake: After Renesmee's birth, there are two smudges of blood on Edward's right cheek. While Edward works to transform Bella, the blood spots appear and disappear between shots.
Continuity mistake: When Edward transforms Bella, he bites her neck first, then her arms, and so on. In the very next close up of Bella, there are no bite marks in her neck at all.