OK, I'm not a breeder, so about the only thing I know about is what we experienced when Ruby had her two foals, and what I've read/heard, so I'll apologize if I say something stupid.
Question: is it true that a pregnant mare will hold off on having her foal if she's continually disturbed by people/other horses?
Details: One of my friends has a mare who is pregnant. She's apparently shown all the signs of being ready to give birth (nearly a week ago), but has not. The mare is being kept in a stall with other horses in neighboring stalls, and my friend checks on her every three-four hours (all through the day and night). She tells me that the mare's udder is sore, and so she won't let the foal suckle, and that's why she has to check on her. There is also a baby monitor in the barn.
It's probably none of my business, and I could be way off base with my assumptions, but at the very least I may learn something.