You talk about how anal sex can lead to pregnancy if sperm gets near the vagina or vulva. How would that happen? Does it have to be on it?
Pregnancy can only happen if semen gets inside the vagina. Since your anus isn’t connected to your reproductive organs, anal sex can’t directly cause pregnancy. But it’s still possible for semen to get into the vagina during anal sex — if the guy ejaculates into or near the anus, and the semen leaks from there down onto the vulva. Fingers and hands could make this more likely, too, by moving semen towards the vulva.
Wearing a condom during anal sex can help prevent any accidental spillage. Besides the risk of pregnancy, anal sex is also a high-risk behavior for spreading many STDs. So wearing a condom is always a good idea. Just remember to use a new condom any time you switch from anal sex to vaginal sex.