Horse Pregnancy Symptoms and Stages

Mating, the gestation period, and foaling are some of the fundamentals of equine reproduction and horse pregnancy. A mare (or female horse) may usually give birth to one viable foal every year. A mare can have a foal at around 18 months of age, but it is healthier if the mare is at least 4 years old, as she will have attained her full size. A mare can have offspring until she is in her late twenties.

Although horses can mate and give birth without the assistance of a veterinarian, many difficulties can be avoided with the assistance of a veterinarian. The doctor can examine the stallion before breeding and monitor and care for the mare during the gestation period.

Gestation Period on Average

Horses normally have a gestation length of 330 to 345 days or 11 months.1 Some mares will foal earlier or later than the average, and breeders will learn about these trends. In the wild, the stallion will breed the mare in the summer, and the foals will be born the following spring or early summer. This guarantees that the foals are born when the pasture is plenty and the weather is pleasant.

Mares are seasonally polyestrous, which means they go into heat (estrus) and are receptive to a stallion at frequent intervals during the spring and summer.2 These seasonal estrus cycles occur every three weeks. Breeders that want to modify the reproductive cycle so that foals are born earlier in the year (as is usual in the Thoroughbred racing industry) will employ artificial illumination to replicate the longer days of spring and summer. The artificial daylight stimulates the brain of the mare, causing it to release the reproductive hormones required to induce estrus. This enables mares to be bred sooner, resulting in a foal early the next year.

Pregnancy Screening

Mares may not display any obvious signs of pregnancy for the first three months, despite the absence of an estrus cycle. Ultrasound can confirm pregnancy around two weeks after breeding.3 Two to three months following conception, blood, and urine tests can be performed. Alternatively, a veterinarian using rectal palpation may be able to feel the little embryo in the mare's uterus. This can be done at six weeks into the pregnancy, and in some cases even sooner.

It is critical to get the mare evaluated by a veterinarian early in the pregnancy to assess her and her foal's health. Horse twins are uncommon, however, they can result in spontaneous abortion. If the twin foals are carried to term, both may die. As a result, it's common practice to "pinch off" one embryo. This is done at a very early stage of the pregnancy. It is relatively uncommon for a mare to lose a pregnancy, so an ultrasound and blood or urine test should be performed after around three months.

Don't Believe Myths

The way a mare shakes her head, the look in her eyes, or how a needle moves when held over her tummy are not reliable indicators of pregnancy.

Gestational Stages Later

After roughly three months, the foal will be fast developing and will resemble a little horse. The mare may become pregnant after about six months. Mares that have previously foaled may exhibit an enlarged abdomen sooner than a novice mare. As the foal near the foaling or due date, the mare's abdomen will continue to develop in the final months. The mare's udder will begin to grow three to six weeks before the due date, and the teats will discharge a sticky yellowish fluid a few days before giving birth.

After about 315 days of pregnancy, an owner should keep a watchful eye on the mare for indicators of impending foaling. The yellowish fluid, for example, will transform into the first milk or colostrum. The udder may drip, and the muscles surrounding her tail head may loosen. As the foal postures for birth, her tummy may appear to decrease.4 Birth is imminent at this point, and the mare must be monitored for symptoms of foaling regularly.

Shortly before birth, the mare will appear restless, pawing the ground or continuously looking toward her flank (hip) area on either side (symptoms akin to colic). She should be stalled in a big, clean stall, preferably with straw bedding. The mare may frequently lie down and get up, but she will most likely give birth while lying down. The amniotic sac should be visible first, followed by the foal's front hooves and nose. At this moment, the foal is usually delivered within a few minutes.

A foal may occasionally be in the 'breech' position. Occasionally, the mare or foal is damaged during the delivery process or has other complications that necessitate immediate or professional attention.

What Exactly Is the Breech Position?

When the foal's hind limbs or quarter are delivered first.

Horse owners should be wary of a "red bag" delivery as well. This is a life-threatening situation that cannot be postponed (not even until the arrival of the veterinarian). A pale, transparent membrane should first develop through the mare's vulva during proper foaling. This membrane should completely cover the foal. If, on the other hand, a brilliant crimson, velvety membrane emerges from the mare's vulva, this signals that the placenta has prematurely detached from the inner lining of the uterus.