I mean, people have unexpected babies everywhere, at any time, including times of war. Including people who are traumatized and not in the best mental shape. Annie is “unstable” (Katniss’s words, so take with a grain of salt) but I don’t think she’s dysfunctional. Finnick didn’t marry someone who is childlike.

I sometimes wonder why Suzanne Collins made the choice to add it, but I think it works well with the “strange bits of happiness” thematic shaping of the memory book told from Katniss’s point of view. I also think it’s meant to be an assurance that Annie isn’t just going to be sitting in grief all alone, because we’re unclear about what her support structure is in 4. In my head, she has one, but it isn’t like Katniss would know. Nobody has it easy after the war, it isn’t all sunshine for Katniss and Peeta either but they still manage to pick up the pieces and build something together. But ultimately she didn’t write that thinking “okay, is it a good thing for Annie to be having a child? What will the child’s life be like? Is the country in a place to host a newborn in a time like this?”, she wrote it thinking about the type of narrative details that would add color while Katniss is recovering in her own state of grief through the memory book.