Are you male or female? Did this happen to you? Chlamydia and gonorrhea can be spread through vaginal fluid, yes. Trich is a parasite that can be spread through vaginal fluid as well.
I realize you're are asking for the guy's information, but if you happen to know the woman and she is not on birth control, you might tell her that there is also a slight risk of pregnancy this way. It is not a big risk, but she should watch and if her period doesn't come, take a pregnancy test.