Line 3
A melon strolling on two tendrils.
Here, the imagery starts to tip us off in a more direct way that this riddle is leading to pregnancy.
Think about a giant melon, walking around on top of two tendrils, a word which, by the way, has a couple meanings. Tendrils are like the leafless vines of plants, reaching up around a fence post or tree, but the word can also be used to describe anything that's delicate and curly, such as tendrils of hair.
Now that you have a clearer picture of what tendrils are like, imagine a big old watermelon strolling, or walking leisurely on top of them. This is a pretty dicey image; we can imagine the melon tumbling off the tendrils at any bump in the road.
And when you add to that the fact that this image is also an example of personification—the melon is given the human ability of strolling—it gets downright funny and playful.
Take the next step and imagine a pregnant woman as this precarious melon: a giant belly on top of normal legs, trying to walk around but slowed down by the child in her womb. It's a playful image, sure, but it also shows just how precarious a position this woman is in.
Line 4
O red fruit, ivory, fine timbers!
Now that we've thought about melons, we move to a different kind of fruit, which we know only as red fruit. When we think about red fruit, we think of something ripe and round like a tomato, an apple, or, perhaps, like a pregnant woman's belly.
We imagine that this fruit is just begging to be picked off the tree. In fact, it's something we'd like to take off the tree, and which we'd probably enjoy eating.
This is a little creepy when we realize that this red fruit, too, is a metaphor for pregnancy. After all, when someone bears children, people say that they're "fruitful."
We move from this red fruit to other desirable and valuable items—ivory and timbers. Remember that elephant from line 2? Well we're betting it had some ivory that a fair few poachers were seriously coveting.
And the fine timbers could be timbers that you'd get from logging and use for a particularly nice hardwood floor, or fancy furniture. Someone's timber, though, could also mean their character. If someone is of a fine timber, then they're a good person.
The weird thing about this line is that, other than the whole being fruitful thing, it doesn't seem to connect to pregnancy that much. But then we think a little harder, and we realize that perhaps this part of the riddle is telling us that pregnant women could be just like red fruit, ivory, and timbers—desirable and expensive.
They're also things that are harvested for someone else's gain. The speaker seems to think pregnant women are objects of greed, and in a way, consumer commodities. This line could be saying that a pregnant woman is desirable to have not as a human being, but as a thing—a sort of baby-making machine.
Also note the emphasis of this line, which is started with an attention catching "O" and ended with an exclamation point. Somehow, though, we get the feeling that this excitement may be sarcastic. Or maybe it's a woeful O.