I’m racking my brain for famous historical or mythological pregnant women. They are hard to find indeed! The virgin Mary is by far number one. No competition. But from there on down, they sharply dwindle in renown.
But there is always the possibility of going as one of Jupiter’s objects of desire, with your male partner in the guise of the form that Jupiter took for the deed. Here are some examples:
1. Europa and the white bull.
2. Leda and the swan. Note: try to avoid looking like Bjork’s famous catastrophe.
3. Semele and a torn heart.
4. Callisto and Diana.
5. Danae and the shower of gold.
There is also the possibility that you could modernize the theme, and go as some made up Greek beauty. For example, you could be Preggynae and have your husband/lover/father of your child/partner/whatever dress as a bottle of beer or expensive consumer item. Whatever form your seduction took.
None of these are really my style. But I’m throwing them out for whoever would be interested.
In the meantime, I will struggle to recall more famous Halloween-costume-worthy pregnant women.