I think it's Maya because she was always upfront / careful about "pulling out" and there's an option at one point to pull out and finish on her pu$$y lips and she makes a comment something like: "This is ok right?has to be a girl which has nothing to do with MC, cause even if you dont fuck ANY girl (and yep this is possible) the pregnancy test will occur. I dont think DPC will make this kind of huge mistake, and i dont think he would do a "random pregnancy" either so he has to write it depending on the choices the MC made.
MAYBE just maybe a girl will blame the mc to be the father, just to cause drama, but no... it will not be the MCs child. Another theory is thats the pregnancy test of lynette, so a flashback, but that would be lame.