Game or real life, the answer is the same: 19-35. Some women look even better, at least in that 4-6 month period where the belly is bigger but not huge.
As young as possible, before double digits if possible. Love to see a classroom full of 4th and 5th grade school girls walking around with pregnant bellies.
18, so when her son/daughter turns 18, the mom is still young enough(36) that they can have sexy scenes together. Wish more games would have pregnancy followed by a time skip to adulthood.
I'm not really a MILF fan so when mother characters are over 40 I have zero interest