How can you tell if a mare is in foal? Only a vet can tell you for sure if a mare is in foal. A vet can ultrasound, palpate (feel), or blood test to confirm a mare is or is not in foal. If you know a mare well and know her heat cycles, one less precise way to tell if a mare is in foal is to watch and see if she comes back into heat. A in foal mare will not show to or tease a stallion.
Do not rely on the size of a mare’s belly to let you know if a mare is in foal or not. A round looking belly can also be caused by worms or other health problems. If you want to know whether a mare is in foal it is well worth a vet visit to confirm she’s in foal and get the mare proper care.