Pregnancy wasn't programmed in this version (0.16.1) probably, but if you follow the correct route it shows that you had sex during her ovulation days (animation of sperms moving towards the ovulated egg ).The thing is that Sasha is part-time and only covers Maria on a Tuesday, when Maria is due to give birth she takes a week off and Sasha covers every that week, so more opportunity to fuck her. Problem is that Sasha's ovulation day is fucked up, so not sure you can even get her pregnant, there also doesn't seem to be any other times so far that you can fuck her.
Maybe Sasha's first kid will arrive next update, we still don't know (until Megalono writes his plans for next version).