Well... I'll spoil that it is most likely not exactly "pregnant". A lot of vore art draws inflated bellies for after the (physically impossible) full-body consumption. Sometimes with a limb or few pushing out against the belly. So I could see how it could easily be mistaken for either pregnant or overweight women.

It is also a common overlap with furries (well- yiff rather) but I guess that makes a bit more sense since animals are more known to eat one another - although it's mostly the anthromorphized ones so idk really.

Also overlaps with the oversized giant women / shrunken male fetishes which I guess makes the act more physically possible if you ignore the impossible sizes of the people involved.

Most vore is "swallowing whole while alive" and not "actually eating", there is often no chewing involved or depicted. If the victim is chewed or killed in the process - that crosses into the less popular guro and snuff categories.

Or perhaps simply scanning the first page of Google image results is not a reliable way to figure out what a weird sex thing on the Internet is actually about.