Originally posted by RandyGiles
I know that vampires cannot reproduce, but when Buffy and Angel first had sex, she did not know that he was a vampire, so she should have used protection. Angel probably knew that nothing could happen, but it is unlikely that she told Buffy. ("Don't worry baby, I'm sterile" might have killed the mood.) I was just pointing out that as far as Buffy knew, she was having unprotected sex with a fertile human, which could be dangerous.
Sorry, but this brings up another question. Can vampires carry STDs? Angel spent a two hundred years life whoring and raping, so it seems likely that he would have caught something. It might not have killed him, but he could have passed it on to Buffy. Darla had a syphilitic heart condition when she turned human, so does that mean that she had been carrying syphilis all of those years as a vampire? If so, she probably would have passed it on to Angel, so he could have passed it on to Buffy. Just a thought.