Signs Of Foaling
Signs that a mare is about to foal can vary from mare to mare, and not to mares are a like, but here are some general signs that a mare is about to foal:
2 - 6 weeks prior to foaling the udder will start to swell
Teats fill 4 to 6 days before foaling
Relaxation of the croup muscles, tail head, buttocks and lips of vulva, 7 - 19 days prior to foaling.
Waxing, 2 - 4 days prior to foaling. Waxing refers to the colostrum (first milk) that drips and dries at the end of the teats. Waxing only occurs in approximately half of mares.
The mare may become anxious and restless. She may exhibit signs of colic such as biting or kicking her belly. She may also lay down and get up again repeatedly, raise her tail and urinate frequently, and sweat. This behavior should not last more than an hour or two without progress toward foaling
Often, if it is a mares first time foaling, her udder will fill, shrink back to normal and then fill again repeatedly. Sometimes a mares udder will not fill until after the foal is born.
If it is your mare's first time foaling, take note of her behavior and keep a record. Mares tend to follow the same pattern year after year. Observing her behavior this time will help you better predict when she is going to foal next time you breed her.
Taken From Ultimate Horse