Representing pregnancy on LEGO minifigs without a dome
The best piece to represent a round belly is the "Plate, Round 2 x 2 with Rounded Bottom" (part 2654). The "dome" pieces are way too big. Connect the rounded bottom plate to the bottoms of two "Brick, Modified 1 x 1 with Headlight" bricks (part 4070), also known as the Erling brick. Use short legs to get the total height right.

Note that the pegs on the leg pieces are slightly larger than a normal stud, so they make for a very tight fit in the back of the Erling brick. They do fit with some force, and they are difficult to remove.

FYI, I experimented with a few iterations, including one using a 2x2 flat tile on a bracket, and this was the version that had my non-Lego fan wife exclaim, "Oh yeah, that looks good!"