Instructions
Ask the horse's previous owners or others knowledgeable about the mare's history. If you owned her then, consider whether she had access to a stallion.
Examine the sides of the horse before the flank as well as the back of her belly area in front of her udder. As the foal starts to grow within her, those areas will enlarge.
Check for an enlarged udder. The udder expands in size to hold milk about two to six weeks before foaling, and it fills with milk two to six days before the birth. Mare's udders may also swell because of rich grass, false pregnancy and/or infection.
Feel your mare's hindquarters. It feels spongy as the mare begins to prepare for the birth and the vulva expands. Generally, this occurs about one to two weeks before she foals.
Feel her udder for a waxy substance. This occurs one to 72 hours before birth.
How to Determine If Your Horse Is Pregnant Without a Vet
Because of the long interval between conception and birth, horse owners may not even suspect a mare's pregnant status until nearly the end of the pregnancy. Horse pregnancies last between 336 and 360 days. Most of the visible signs of pregnancy occur about two to three months before birth. With a basic understanding of how the mare's body functions during pregnancy, horse owners can make an educated guess.