pregnant mare - huge bag!

Question
Our mare is due to foal any time now, her bag started to fill about 3 weeks ago, it is now absolutely huge! it is rock hard and since this is only our 2nd foal, i am not sure if it is normal since it seems to be 'backing up' into her body, towards the front end for her bag.It seems that the milk is now starting to collect/flow up into her actual body as it is swollen also, about an inch thick.
Is this normal? she seems fine and is snowing no signs of problems but i have never heard of this or seen it before. Please respond and help ease our minds!
Thank you

Answer
Is this her first foal?  Is this mare out in a pasture or confined to a small area?  Is the swelling soft and if you gently poke it with a finger does there remain a depression?  If there is a depression it is called pitting edema and you should hand walk the mare at least twice a day to help resolve the excess fluid.  It sounds like she is getting close to foaling so you should watch her closely.  If it will not upset the mare, you might also spray her stomach (always spray water on the hoofs first so the horse gets used to the water temperature before spraying the body) and udder.  Be sure not to use much pressure from the hose.  It needs to be a very gentle spray.