Nothing. A little messy, but not terrible. If it grosses you out, then don't. If you are OK with it, then put a towel under the action.
The only medical downside is that if there are any blood born diseases involved, they have a really good pathway for infection. If you are long time monogamous, then no medical downside.
you can still get pregnant you can still get stds/stis the only thing that might be awkward is the blood people still have sex on there period though, if your worried about getting it all over the sheets put a towel under you but your period wont protect you from pregnancy or diseases
Nothing. It's just a little bit...bloody. lol.
Nothing, its just a little grosser!
It's Messy X(
more mess, and blood!