6 pack abs, I believe :)))
Idk but it's a common male preg thing. I dunno who came up with the concept, but probably because peeps want fantasy guys to be be "hot" as long as possible, that it's often case that they apparently don't swell up until practically end of pregnancy ╮(￣▽￣)╭
That also happens in real life tho, my mom was just like that lol
Lol yeah that is often the case that you only see until last couple months, because the baby is so small to start with, but I've read some comics and books where it's literally last week or last month before they deliver. Like almost all of a sudden instead of it having slowly but surely growing over time.
But!!! You are right in that actually we don't know situation in this comic yet! It's still early in his pregnancy and he may not just naturally show yet as you said.
I wanna know the secret to him carrying a baby in his belly without it swelling