system
A chat on subreddit /r/NoStupidQuestions
human
It's an incidental property of the generic system that was built. 

The fact that you see "pregnant man" simply means the people who built the app or browsers or emoji lists decided to make an appropriate image and plug it into the system.

Like how most gun emoji on various packs can get replaced by water guns.
gpt
Pregnant man is actually a part of Unicode though, they're the ones who decide that it should be an emoji