Semen, the fluid that carries sperm out of the body, is not alive. The sperm are the tiny swimmers in the semen that can cause pregnancy, and they are indeed alive for awhile out side the man's body.
female vamires cant get pregnant because their bodies have to change in order to do so. males don't have to change to roduce sperm so if edward had sex with Bella, they would have a kid cause Bella's...