I think her pregnancy progress is bugged. For one I never saw her pregnant bust again (after the initial one). Second I skipped ~80 days from (3021 to 3103 in my save) - I only periodical checked Maternity Duty -> Me - Pregnancy option is always grey out with description: "You can't opt out while Lumia is pregnant". Save without party members and in Lumia palace on day 3021 in attachments.
Scene that confirms her big belly and normal bust:
Scene that confirms her big belly and normal bust:
