A lot of folks have mares that have been bred and are out to pasture waiting for the lil' ones to develop and be born. That'll be a joyous day for you when it happens.. IF all goes well.
There's a lot of things that can go wrong, but one of them that can go wrong is often never even heard of until it happens to the owner's mare. the problem lies with the notion of endophytes in fescue grass.. some of the problems it can cause are
thickening of the placenta to the point where the foal can't break through it and suffocates.
low or no milk (and there for colostrum) production
delayed foaling, however, the foal continues to grow and winds up having to be delivered by cesarian section, or pulled (which is hard and sometimes fatal to the mare) or cut into sections in the womb and removed that way.
The simplest way to prevent this from happening to you is to make sure your mare is off of fescue grass or fescue grass hay at least three months before her due date.
I've seen too many folks in the Ozarks have that happen to them, and they are not stupid, just unaware. Don't let ignorance do you harm.