No. Stephenie has answered this multiple times alongside the period question. A vampire’s only bodily fluid is its venom, this replaces the saliva. Thus, vampires have no sperm, so they cannot make vampire babies. Also, when a vampire is changed, they stay the same way forever. Frozen. If a woman is pregnant, she will remain pregnant forever, no matter what stage her pregnancy was in, two days or eight months.

This also explains Alice’s hair. Before she was changed, she was in an asylum, so her hair had been shaved off, and it was just growing back when she was changed. If you have long hair, and you are changed then you cut that hair, it will not grow back. If you have split ends, tough luck. They can style their hair though, like get hair extensions, or use curling and straightening irons.