belly cast
n. A plaster cast of a pregnant woman's stomach.
Mothers-to-be nationwide are getting plastered, with belly casts appearing at baby showers as gifts, said a Maine businesswoman who sells the molding kits.
—Dawn Sagario, “Moms-to-be keep their bellies,” Des Moines Register, August 21, 2001
1993 (earliest)
The items I'm looking forward to seeing bid on are the wild ones that could only turn up at a feminist free-for-all. How about a 'belly cast' of your eight-month pregnant abdomen, crafted by an artist?
—Michele Lansberg, “Auction is a delightful feminist event,” The Toronto Star, November 16, 1993
This phrase — which I first spied in a flyer tacked to our local coffee shop's community bulletin board (do you see the extra pains I take to bring fresh words to you people?) — originated as an example of birth art, which I'll talk more about tomorrow. Nowadays it just seems to be a bit of a fad, with some women actually getting the casts made at their baby showers! Another term for this is bellymask (coined in 1986).