The fact that Catherine will die in childbirth is foreshadowed well before the reader gets to the final chapters of the novel. But Hemingway was wise to include this foreshadowing because the focus of the novel needs to remain on the protagonist Frederic Henry. If the reader gets consumed by wondering whether or not Catherine will make it safely through childbirth, then the focus of the reader's attention is not in the right place. At this point, the important dynamic to consider is how Henry will handle the death of Catherine, especially given the fact that it is his relationship with her that seems to give him a sense of purpose. In terms of the inner workings of the story, Catherine has to die in order for Henry to be put to the test. So, foreshadowing Catherine's death prepares the reader to continue to follow Lt. Henry's journey as the protagonist and not to get de-railed by concerns over Catherine.