After a gestation period of about 11 months, a horse will typically give birth to her foal during the night. The foaling process can last for around eight hours, though labor is often shorter, and most mares will manage without any human assistance. However, an equine labor has three stages, and being aware of how long each one can last is important for knowing whether, and when, a veterinarian should be called.
The First and Longest Stage
The first stage of labor can last one to four hours. The mare, if she feels threatened, perhaps sensing predators or bad weather, is able to delay labor at this point by hours or days. Also, it can be hard to tell when this stage starts. This is because most of the action is happening in the mare's uterus as her foal moves into the birthing position. When the initial uterine contractions begin, the mare may grow restless, pace and break into a sweat. Other outward signs of labor include frequent urination and defecation, holding up the tail and looking back at the flanks. These signs are usually short-lived and the mare may not display any of them. They can also be an indication of colic. A mare can get colicky before foaling if she is constipated, so if the signs are severe or persist for hours, call a veterinarian.
Fast and Furious
When the mare's waters break, releasing 2 to 4 gallons of amniotic fluid, the second stage of labor starts. The foal's entry into the birthing canal stimulates stronger contractions and the mare typically lies down, straining as she attempts to push her foal farther into her pelvic opening. Before long the foal's front feet should appear, one slightly before the other, followed by his muzzle, head and chest. The foal's movements usually break the fetal membrane, and within a minute the foal should be breathing. This stage of labor is fast, taking only five to 15 minutes; if the foal doesn't appear within 20 minutes from when the mare's waters break, a veterinarian should be called immediately, as the foal may be wrongly positioned.
Once the foal's head and shoulders have emerged, the mare will stop pushing for a short while before the hips and hindquarters slip out. At this point the mare will take a longer break, possibly for up to 40 minutes. This resting time is important as it helps to prevent the umbilical cord from breaking before the last of the blood supply from the placenta flows to the foal. It may also protect the mare's uterus from infection. When the mare finally stands up, the now-brittle umbilical cord will generally break in the correct place and is less likely to get infected or bleed from the stump.
Expulsion of the Afterbirth
After delivery, further contractions help to expel the placenta or afterbirth from the mare. This is the third stage of labor and may happen within minutes of the foal's arrival, but can take up to three hours. If the placenta isn't expelled after three hours, a veterinarian should be called straightaway as the afterbirth needs to be removed within six hours of foaling. Otherwise it may cause a serious infection and such infections can lead to laminitis. If the placenta is expelled within three hours, it should be examined for holes. Even a small piece of placenta retained in the mare's uterus can result in an infection.
- The Complete Equine Veterinary Mannual; Tony Parvord BVSc, MRCVS and Marcey Parvord
- Colorado State University Equine Reproduction Laboratory: Foaling Fundamentals
- Gaited Horses: The Foaling Mare Management Guidelines
- America's Horse Daily: Stages of Labor
- Aldington Equine Vets Ltd.: Foaling Facts [PDF]