Horses Horse Health & Wellness

Horse Pregnancy: Signs, Stages, and How to Care for a Pregnant Mare

An illustration of the stages of horse pregnancy

The Spruce / Melissa Ling

Horses can become pregnant as early as 18 months of age and their pregnancies last around 11 months. If you think your horse is pregnant, she'll need proper care from the beginning of her pregnancy to optimize both her health and the health of the foal. Here's what you need to know about the signs and stages of horse pregnancy and how to care for your pregnant mare.

How to Tell a Horse is Pregnant

The only way to be sure that your mare (female horse) is in foal and that the pregnancy is progressing normally is to have her examined by a veterinarian, preferably one who specializes in equine reproduction. This should be done about 14 to 18 days after the mare has been bred.

Pregnancy can be confirmed by ultrasound approximately two weeks after breeding. Mares should be examined for twins by ultrasound at day 15 or 16. An earlier exam may miss a twin that is too small to be seen. Blood and urine testing can be done two to three months after conception. Alternatively, a veterinarian may be able to manually feel the small embryo in the mare's uterus via rectal palpation. This can be done at approximately six weeks into the pregnancy and sometimes even earlier.

Don't Rely on Myths

There are several folk methods and theories to determine whether your mare is carrying a foal or not, but these are neither reliable nor accurate. Checking how a mare shakes her head, the look in her eyes, or which way a needle moves when held over her belly are not accurate methods of determining if she is in foal.

Signs of Pregnancy in Mares

Beyond the absence of a heat (estrus) cycle, mares may not show any visible signs of pregnancy for the first three months. Plus, the lack or presence of a heat cycle is not a sure indicator of pregnancy. Some mares will appear to have a heat cycle despite being in foal because of increased estrogen levels.

  • About three months into pregnancy, the foal will be developing rapidly and start to look like a small horse.
  • After about six months, the mare may appear visibly pregnant.
  • Over the remaining months, the mare's abdomen will continue to grow as the foal approaches the foaling, or due date.
  • About three to six weeks before the due date, the mare's udder will start to expand.
  • A few days before giving birth, the teats will produce a sticky yellowish fluid called "wax."

Not all mares show obvious signs of being in foal, even late in the pregnancy. Some mares, especially those that have not carried a foal before, may not 'show' much at all. Others have a well-sprung barrel that looks like they are in foal all the time. This can be because they’ve had several foals before, or it may be because the mare has a hay belly that makes her abdomen look distended. There have been situations in which an owner had no idea that the mare was in foal until the foal arrived.

How Long Are Horses Pregnant?

The gestation period in horses is typically between 330 and 345 days, or 11 months. Some mares will be inclined to foal earlier or later than the average, and breeders will get to know these tendencies.

A mare can typically produce one viable foal per year. Though capable of pregnancy at about 18 months of age, it's healthier if the mare is at least 4 years old as she will have reached her full size. A mare may continue to have foals until she is in her late 20s.

Horse Breeding

In a natural environment, the stallion will breed the mare in the summer, and foals will be born the next year, in spring or early summer. This ensures that the foals are born when pasture is abundant and the weather is mild.

Mares are considered seasonally polyestrous, which means they go into heat (estrus) and are receptive to a stallion several times at regular periods during the spring and summer. These seasonal estrus cycles are approximately every three weeks.

Breeders who wish to manipulate the breeding cycle so that foals are born earlier in the year (commonly done in the Thoroughbred racehorse industry) will use artificial lighting to simulate the longer days of spring and summer. The artificial daylight stimulates the mare's brain to produce the reproductive hormones needed to induce estrus. This allows mares to be bred earlier, and in turn, have a foal earlier the following year.

How to Care for a Pregnant Mare

If your mare is pregnant, you'll need to adjust her care and feeding to support the pregnancy. The first step is to contact your veterinarian.

Veterinary Care

Your mare should be checked by a veterinarian early in the pregnancy to assess her health and the foal's health. Although horses can mate and give birth without the attention of a veterinarian, many problems can be circumvented with a veterinarian's help.

While it's important to maintain a regular vaccination and deworming schedule throughout the pregnancy, your mare shouldn't receive these medications during the first two to three months. Some vaccines and parasite control medications can interfere with fetal development. Your veterinarian is the best source for advice about which medications are safe to give your pregnant mare throughout her pregnancy.

Although it costs money to have your mare properly examined by a veterinarian, the expense is negligible compared to the cost of raising a foal—or losing a foal or the mare. Raising a foal can be one of the more expensive ways of producing another horse.

Twin Foals

Around 14 to 18 days into pregnancy, a veterinarian can determine if the mare is carrying twins. Horse twins are rare but can lead to re-absorption and spontaneous abortion. If the twin foals are carried to term, the chances of a mare surviving the birth herself and successfully producing strong twin foals are slim. For this reason, it's often recommended to "pinch off" one embryo to give the other embryo a better chance for normal development. This is done very early in the pregnancy.

The mare should be checked again at regular intervals, as determined by the veterinarian, to ensure that she's still in foal and there are no uterine infections that need attention. The vet can confirm whether the pregnancy is progressing normally and how advanced it may be, so you should know at a fairly early stage whether there might be any complications.

Feeding a Pregnant Mare

Your pregnant mare should have high-quality hay or pasture, salt, and minerals. If your pasture grass contains fescue, you may want to remove the mare 60-90 days prior to foaling to avoid fescue toxicosis and allow her to graze elsewhere. Only late-term pregnant mares are susceptible to the ill effects of grazing tall fescue. You may want to separate your mare from any pasture bullies that could cause her harm or injury, and thus make the foaling process more difficult for her.

Can You Ride a Pregnant Horse?

Yes, if your horse is accustomed to this, it's usually safe to ride them up and exercise them as normal for the first five months of pregnancy. In general, light riding is safe until the last month of pregnancy. Exercise is beneficial for most pregnant mares, so be sure to provide turnout if they are not being ridden unless your veterinarian recommends otherwise.

Preparing for Birth

After about 315 days of pregnancy, an owner should watch the mare closely for impending signs of foaling:

  • The yellowish fluid from her teats will turn into the first milk or colostrum.
  • The udder may drip, and the muscles around her tail head will become more relaxed.
  • Her belly may appear to drop, as the foal positions for birth.

At this point, birth is imminent, and the mare must be checked frequently for signs of foaling.

Shortly before birth, the mare will appear to be restless, she may paw the ground, or repeatedly look toward her flank (hip) area on either side (similar to colic symptoms). She should be stalled in a large, clean stall, preferably ​bedded with straw. The mare may lie down and get up repeatedly, but she will likely give birth lying down. First, the amniotic sac may be visible, and then the foal's front hooves and nose should appear. The foal is normally delivered within a few minutes at this stage.

Complications

Occasionally, a foal is in the 'breech' position. Sometimes the mare or foal is injured during the birthing process or may have other issues that require urgent or professional attention.

What Is the Breech Position?

When the hind limbs or quarter of the foal is delivered first.

Horse owners should also be aware of placenta previa, often called a "red bag" delivery. This is a critical emergency that cannot be delayed (not even for the arrival of the veterinarian). During normal foaling, a whitish, translucent membrane should first appear through the vulva of the mare. This membrane should encase the foal. If, however, a bright red, velvety membrane appears instead, coming through the vulva of the mare, this indicates that the placenta has prematurely separated from the inner lining of the uterus.

The placenta supplies the foal with oxygen, and if this becomes prematurely separated before the foal can breathe on its own, the foal would be deprived of oxygen. This can lead to various neurological effects or the foal may even suffocate. Every second counts in such cases and the mare must be manually assisted in the delivery of the foal. The red bag must be ruptured immediately to allow the foal to breathe.

For every foaling, your veterinarian should check both mare and foal carefully shortly after the delivery.

If you suspect your pet is sick, call your vet immediately. For health-related questions, always consult your veterinarian, as they have examined your pet, know the pet's health history, and can make the best recommendations for your pet.
The Spruce Pets uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.
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