Ahh, but that would be visuals. Not consequences. No problems there. Like allowing beards on female characters in customization.
The requests for "pregnancy" I saw and see in comments are usually not asking for visuals of a customizeable character alone ;-)
I do not know about Steam, but Patreon might kick you for having certain pregnancy content. I remember a game where the creator made the female mc lay eggs instead of babies for that very reason. It was also a magical pregnancy that lasted for ingame days, not months.