In "What’s Up with the Title?" we break down the literal meaning of the components of what is for many the story’s key symbol – the "hills like white elephants." In "Setting" we talk about how this symbol can be used to interpret the story. Here, we’ll go with that while playing with the idea of wildlife.
Elephants are wildlife. Jig and the man have been living the wild life, but now it could all come to come to a halt – like it has for the white mountains. But are mountains happy in their stability?
Who knows, but the man doesn’t want to be a mountain, be married and settle down (and he thinks that Jig having the baby will mean he must). Jig, on the other hand, thinks they can only remain in motion, wild and free, is if they do have the baby and get married.