A game that I found an almost ideal Pregnancy mechanic is Summertime Saga, its MC can get most women pregnant, however, only two out of many can have sex during Pregnancy, the others unfortunately do not have sex while pregnant...
But regardless of that, after the children are born they are sent to a day care center where you don't have to worry about them. (which for me is ok, because my greatest pleasure is in getting the characters pregnant and having sex with them while pregnant, if possible, indefinitely, I cited this example as a pregnancy mechanic to be adopted...).