What sort of pregnancy is going to be implemented? Is it story focused? Is it side content? Will it go by quick by a few weeks or months? Is it long term, like 6-10 in-game months? Will there be interactions with the character during said pregnancy? Do the characters behave differently? Will it add an extra layer of difficulty? Will it show gradually? Will labor be a factor in the game? Will we see it as it happens or will it be offscreen? Will it happen automatically or require something to trigger it? Will becoming a parent be part of the experience?
I will answer a bit vague, as I don't want to spoil the story to much. But certain characters, will be pregnant, you will see it and you will interact with them (Lactation and pregnant sex is planed). At least that's what I've planed, but be aware, this won't be anytime soon. It will be a regular term, but you won't play day by day to the end. It will be story dependent and probably a few months will be fast-forwarded.
I don't plan pregnancy to be the end of the story and wan't to continue afterwards. But in all honesty, that's so far in the future, it isn't fully fleshed out yet. But parent-hood will be part of the story.
"Do the characters behave differently?" => Probably... Too far in the future to be specific about it.
"Will it add an extra layer of difficulty?" => In terms of relation management? Not sure yet. Would make sense. Depends on how complicated it will be for me to handle the branching.
"Will it show gradually?" => In steps probably. Everything else would be to complicated.
"Will labor be a factor in the game?" => It's planned.
"Will we see it as it happens or will it be offscreen?" => Not sure yet. Will be difficult to present "tastefully". Not sure yet, but probably not with 'explicit' content.
"Will it happen automatically or require something to trigger it?" => It will be story dependent, so it won't just pop up.
I know that many people love their harems, but if we're honest, then nobody can deny that those storylines are always pretty cringe in how blatant they are about wish fulfillment. There's nothing wrong with that, but it's always a bummer, when a story that seemed "better than this" ends up as a harem.
Selene is a well-made character, she's just not a typical harem waifu. I think it reflects well on your writing ability that you have a character besides the PC that's allowed to have a backstory and an agenda. Sadly a well-made character has its own personality and this particular personality might not be everyone's cup of tea. But I think it's more important that well-made characters are the building blocks for a genuinely good story.
You are right. No doubts. I don't want to end up in a cringe story and hopefully I won't. I'm well aware that this might be to ambitious but at least I want to try. If I don't find a story where it really makes sense I'll adjust. But at the moment I'll stick to it.