The following art I am posting is well drawn, but still cringe-worthy.
I acknowledge that applying logic here is pointless, but bear with me:
(mpreg)
http://th01.deviantart.net/fs71/PRE/f/2014/056/5/d/commission__you_ve_gotten_big__m_preg__by_kirame90-d781ufl.jpgFetuses grow in uteri. Males do not have uteri. If they did they would technically be Hermaphrodites. Now, I think I remember reading somewhere that a male pregnancy theoretically
could work, but the birth would be fatal, in which case it wouldn't be portrayed as a happy-cutesy thing.




The artist:
http://shydude.deviantart.com/Two problems with a lot of "big belly" art:
A) There is no way their abdomens could get that big.
B) No matter the size, it wouldn't be as smooth as a baby's bottom, there would be stretch marks.
Same thing goes with all other "big belly" art, whether it be vore or stuffing or pregnancy.