In the Twilight series, sex comes after marriage – at least according to Edward. So when Edward and Bella get married, they make love for the first time. Breaking Dawn links sex and danger, at least initially. Before Bella becomes a vampire, sex with Edward poses a serious threat to her. Edward is afraid that he'll accidentally kill Bella, and she does indeed wake up covered in bruises after they first have sex. However, Bella doesn't seem to mind. While Edward is afraid to hurt her, Bella comes up with all kinds of tactics to tempt him into continuing to sleep with her.
Breaking Dawn also explores sexuality as a sensual experience. Because vampire senses are superior, vampires are apparently able to enjoy their sexual relationships more deeply than humans can. At first, however, Bella wants to stay human, because she believes that as a newborn vampire, her thirst for blood will overshadow her physical attraction for her husband. She's surprised to find that after her transformation, her physical attraction for Edward actually increases, because her senses are now able to fully appreciate his body and his mind.