It's hard to describe well, but it's sounding like that to me. Mares go from looking like a beach ball to flat sided (although it's not really flat sided, just a big difference) And the bottom line, front to back goes from gently rounded to almost pointed. There may be a big milk vein in the belly, running back to the udder.
RoS has commented a couple of times today that Sugar looks narrower. That could very well be the case.