Understanding How Long is a Horse Pregnant

Whether breeding for pleasure, performance or show, careful consideration is taken into the whole breeding process. A lot of time, money, research and care are taken into account to achieve the best possible horse. With all the work that goes into breeding, you’ll wonder how long is a horse pregnant.

A Typical Horse Gestation Period

Gestation of a horse typically lasts 10-11 months, from conception to birth. Most mares only carry one foal per pregnancy, though twins do happen on rare occasions. Due to these factors, a horse can only have one pregnancy a year and will generally only have one foal a year.

Horses can have a fairly broad gestation range. They can be pregnant anywhere from 320-380 days. Generally, a horse is pregnant for 330 days, which is 11 months.

How Long is a Horse Pregnant: Gestation Stages

A mare will go through roughly three trimesters during the gestation period. The first trimester begins with conception and is generally confirmed at two weeks. During the first trimester, it is important to have a vet check your mare to track the health of her and her foal.

As early as 26 days, a vet can perform an ultrasound that detects a heartbeat and can confirm vitality. At this time, your vet will be checking to see if the mare is carrying twins. By three months, the form of the foal starts to look like a horse, developing key features and the gender of the foal can be found out.

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The second trimester starts at around day 114. During this time, the mare can begin to receive dewormer and vaccinations. The mares feed should be increased to provide the needed nutrition to the fast-growing foal and by six months, the mare begins to show.

The third trimester comes along at approximately day 226. During the third trimester, it is important to monitor your mare as much as possible. Up until around the seventh month you can regularly exercise your mare.

As your mare nears giving birth, it is important to keep her in a comfortable and stress-free environment. Avoid any big changes, as it might cause the mare to be anxious.

Horse Breeding Season

Generally, horses are bred during summer to guarantee a spring or early summer birth. This allows the foal to have access to fresh grass when it is ready and ensures the foal won’t have to endure cold winter temperatures at a young age. Lots of planning and careful consideration goes into breeding a horse.

How Long is a Horse Pregnant: Gestation Stages

Seasonal Polyestrous: Mare in Heat

The term seasonal polyestrous may sound complicated, but it simply means that horses go into heat (estrus) during the spring and summertime. When a horse is in heat it means that they are sexually receptive and fertile. Heat cycles generally happen every three weeks during the spring and summer.

Some breeders, especially those who breed Thoroughbreds, may try to manipulate a horse’s breeding cycle. They may try to use artificial light to stimulate the longer days of spring and summer to convince the mare to go into heat earlier. This allows the foal to be born earlier in the year, which can be an advantage for racehorses.

How Long is a Horse Pregnant: Twins

Though rare, a horse may conceive twins. Unfortunately, most times both foals do not survive, as horses’ bodies are not built to carry two babies. In many cases, if a horse carries twins to term, there are several complications that can occur for both mother and babies.

In most cases, twins happen because a mare has ovulated twice, one egg from each ovary. It is very rare that identical twins are formed from a split embryo.  

How Long is a Horse Pregnant: Twins

One of the first things a vet will check for when examining a pregnant mare is whether or not she is carrying twins. If twins are found, your vet may remove the second embryo to give the other one a fighting chance. A mare may also abort twins within the first six weeks of gestation.

There are a few cases where a mare can give birth to healthy twins. However, if your mare is pregnant with twins, it is best to consult your vet to ensure a healthy pregnancy for your mare.

How Long is a Horse Pregnant: The Most Exciting Part

As your mare continues on into the third trimester, you’ll need to make sure you are fully prepared for the arrival of the foal. After about day 315, you should carefully watch your mare for signs of foaling, as the foal will likely come around day 330. It’s not uncommon for a mare bred early in the year to carry a week longer and a mare bred in late spring or summer may have a shorter gestation period.

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Signs a Mare is About to Give Birth

In the days leading up to the birth, your mare will likely show signs that she is ready to foal. Her udder will likely look full and may drip some milk. Her belly will likely look like it has dropped, as the foal gets ready to come out.

It is best to give your mare a large stall, covered in straw, with access to freshwater and hay. This will give the mare a comfortable place to give birth.

As the mare begins to go into labor, she will likely paw the ground and appear restless. She may get up and down a few times, but she will give birth laying down.

The amniotic sac is generally the first part visible, followed by the head and legs. Once the amniotic sac is visible, it is generally a few minutes until the horse is born.

A Beautiful New Life

Having a foal arrive is a truly exciting time. Generally, within an hour of the foal being born, it will be able to stand up and shortly thereafter, walk around. Within two hours the foal should be contently nursing.

It is always a good idea to have your vet there when your mare goes into labor. Your vet will be able to help with anything that may go wrong during birth and assess the health of the foal once it is born.

How Long is a Horse Pregnant: The Most Exciting Part

Worth the Wait

Though a horse is generally pregnant for 10-11 months, they still may give birth to a healthy foal before or after that time. It is important to provide your mare adequate care during this time to ensure a healthy foal.

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