I wouldn't hold your breath for any sort of universal system where any of the girls can get preggers, or multiple at once. I suspect it'll be more like Myrtle or Holly getting a specific "pregnancy arc" which is basically an on-rails cutscene and then afterwards they're back to normal and the kid goes to live with the fairies or something. That would still be fine but it's not what I typically picture when I think of a game adding pregnancy as a "mechanic" so I wanted to encourage you to lower your hopes a bit right now so you won't be too disappointed.
