Size

Size matters when you're pregnant. It just does. And it definitely matters to our speaker. We never hear directly about a woman's huge belly, but we hear about elephants, houses, melons, and all sorts of big things that make us visualize pregnancy in a whole new (big) way.

• Line 2: This line uses both an elephant and a ponderous (huge and heavy) house as a metaphor for a pregnant woman. Hey, we never said it was a nice metaphor.
• Line 3: Here, we get a metaphor that lets us see how disproportionate the belly of a pregnant woman is to her body—like a melon on top of two vines. That sounds ungainly.
• Line 5: In this line we hear about a big bread loaf, yet another metaphor for a pregnant woman's belly. This image of size gives us not only a metaphor for the bigness and shape of the belly, but also, through mentioning the bread rising, its growth. It's a one-two punch, figurative language style. 
• Line 6: This line incorporates the use of the word "fat" through using a purse with a lot of money in it as a metaphor for a womb with a baby in it. "Fat" is a new, more derogatory kind of big. A purse can also be used as an innuendo, or a sort of masked sexual reference for a woman's genitals. Wow this speaker just gets more and more (read: less and less) complimentary with each passing line.
• Line 7: Using a cow in calf as a metaphor for a pregnant woman again ramps up the size imagery in this poem. We've seen this poor woman as an elephant, a house, and now a cow? Yikes.