It can be frustrating watching mares and predicting when they will foal. Mares are usually consistent in their foaling pattern from year to year. Therefore, horse owners and managers should become familiar with each mare and record their observations on the mare's record. The average gestation length of a mare (period between breeding and foaling) is 340 days. It can vary within 20 days either side. In one study, 65.5% of mares foaled at night between 8 p.m. and 1 a.m.

The visual signs of a mare's readiness to foal are:

• Udder distension begins 2-6 weeks prior to foaling.
• Relaxation of the muscles of the croup 7-19 days prior to foaling;
  relaxation around the tail head, buttocks, and lips of the vulva.
• Teat nipples fill 4-6 days prior to foaling.
• Waxing of the teats 2-4 days before. Waxing (or wax beads) refers to the colostrum (first milk) which appears at the end of the teats.
• Dripping of colostrum 24-48 hours before foaling. Loss of colostrum may result in an inadequate supply for the newborn foal.
• Prior to foaling, the mare's body temperature will be equal to or drop lower than her normal morning temperature.