Re: how likely is it to get pregnant from precum
I am not aware of very many documented cases of pregnancy resulting from precum. The belief is propagated, and a few women have sworn they got pregnant that way, but the scientific evidence is not there. What science does show is the precum does not contain much, if any sperm, and that it takes a lot of sperm to protect the one cell that might ultimately find the egg. I mean, a vagina is hostile to a few lone sperm cells, and it takes a whole army of sperm to plow though to the cervix and make the journey to the egg. There is simply not a whole army of sperm cells in precum. Maybe a few scouters or stragglers.
So, while it is possible, it is unlikely. The odds might be a bit higher if the guy had previously ejaculated , as there could be a few sperm cells lingering in the urinary tract that could come out in the precum.
I would be more worried about catching an STD.