This kink is great because we take the concept of "pregnant belly get rounder as baby grows" and come up with the most convoluted, overengineered, insanely varied ways for that to happen. How fast does it happen? How long does it stay like that? How much sex made it happen? Is it a human baby or something else? What other side effects are happening? How are we dressing it? How much food does it need? What is the 'hyperpreg' threshold?