Can precum in vagina during period cause pregnancy?

I was dumb enough to have intercourse without a condom, and now I'm worried about the repercussions. Ok, so I think i precummed in her (don't really know because you never really know) and she was on her period. Her period started on the 19th of May. I have masturbated ~30 hours before hand, so it's possible the precum will contain trace amounts of sperm. After the intercourse (about 3-4 hours later) she had a vaginal discharge of blood (due to her period). I did not cum in her, nor was I even close (I pulled out WAAAAAAYYY before). So I was just wondering what were the chances of a pregnancy?