I know that anal sex has higher chances of transmitting HIV for both partners.
What I haven't been able to find is if there are risks of unprotected anal sex not present on unprotected vaginal sex, and which are those.
The baseline would be a couple that regularly practices condomless vaginal sex (with other contraception methods). What new risks would them be exposed to when engaging on condomless anal sex?
I think "asume none of the partners have STIs" is a huge stretch medically speaking, but since that's a risk already accepted on condomless vaginal sex, I'm more interested on any other existing risks.