How Long Are Horses Pregnant?

A mare is ready to carry a pregnancy from 18 months old. However, it is safer if the horse is at least 4 years old. You might want to consult with a veterinary on any potential effects of the pregnancy.

baby horse

So how long are horses pregnant? 11 months is the standard gestation period for a horse. In some cases, it can extend to 345 days. As long as it goes up to a year, you should not be worried. Foals born within 10 months or less are usually unstable and unlikely to survive.

Season affects the gestation period by a week or so. Mares bred during summer or spring tend to have a shorter gestation period than mares bred in the first three months of a year. IN such cases, the delivery can delay by a week. This is still within the period and should not be anything to worry about. As long as you have veterinary close with regular checkups, the foal will be delivered safely and in required health.

Can I influence the gestation length?

Yes. But you need professionals to help you with the process without compromising on health of the mare and foal. The mare can be exposed to longer artificial days in the final trimester. The gestation period can be reduced with 10 days or more. 10 is a big number considering you have been waiting for the whole year.

Natural elements

Breeding season has everything to do with gestation period. It can take a week longer or shorter depending on the time of the year.

Besides, sex of the foal causes variance in gestation periods. A colt takes at least 2 to 7 more days before delivery as compared to a filly. There is no definite scientific explanation to the male and female impact on gestation period but it is always the case.

Body weight and structure also determine gestation period. Some mares are naturally thin and others muscular. Like human beings, some mares gain weight during pregnancy but others do not. Thinner mares carry their foals for a longer period as compared to mares with more weight. The weight effect goes back to the breeding period.

In either case, the maximum gestation period goes up to 345 days, which can easily be broken down to three trimesters for easy monitoring and evaluation of the pregnancy.

What changes do pregnant mares experience?

Just like most mammals, the pregnancy process begins with ovulation. However, this can only be confirmed after ultrasound within two weeks of breeding. A veterinary checks if there is any possibility of twins. If there are two embryos, one is removed to increase survival of the other. Mares can barely carry two foals successfully to delivery. In fact, the twins are likely to aborted in the first 6 weeks. If they luckily survive to the end of gestation, they will be born unhealthy with low weight hence low chances of survival.

Allowing the mare to carry twins is exposing her to greater health risks because it is not natural for an embryo to split to twins. It is better if the process is cut earlier before the 30-day mark. Sex of the foal is determined after 90 days, which is also the first time to deworm.

The second and third trimesters are more of the same. Second trimester begins at day 114 and goes to 225 days. During these two trimesters, the veterinary will increase frequency and amounts of deworming. Also, sex of the foal is re-checked for accuracy. Vaccinations are also suitable in these two stages depending on your location and condition of the foal after various veterinary tests. Also, you will be actively involved in these stages with regards to feeding the mare. Proper nutrition is crucial for healthy development of the foal.

While a standard gestation period ends between 326 to 354 days, arrival day and time of the foal is unpredictable. It is much more uncertain if it is the first time for the mare meaning there is no history. Most breeders have specific test kits for establishing arrival day and time of the foal. However, it is often an estimate of a 24 hour period.

In fact, the test kits are more of when the foal will not arrive. The testing is on basis of magnesium and calcium levels. If the test is negative, the breeders are sure the foal will not be coming at least for the next 24 hours. This means when you get to 320 days you should engage breeders more regularly for monitoring and the tests.

How can I help the mare during gestation?

First, you should make sure the mare is on a proper nutrition diet at least 60 days before breeding. Thin and unhealthy mares strain a lot with pregnancy. Also, an unhealthy mare may not be able to carry the foal to term.

  • Keep it away from other horses that can causes injury or infection to the mare
  • Only transport it if necessary; otherwise, it should always be close to home.
  • If you are feeding her well enough, you won’t need any supplements. Make sure she exercises adequately and feeds normally until the 7th month where you should increase both exercise and amount of food.
  • Include extra roughage in the mare’s diet to avoid ulcers and any gut issues that can affect pregnancy.

Four Stages Of The Foals’ Birth

  • Phase One: The mare will not relax and is completely restless. Might even look like the onset of colic. So laying down and getting up is actually normal. This usually is a sign the foal is coming within a couple hours
  • Phase Two: This is where the water breaks and the fun begins. The mare will usually be standing up with this happens. You should see feet in about 20 minutes may 30 max. So if this doesn’t happen call the vet immediately and start walking the mare until the vet arrives as something may be wrong. That goes for anything that just doesn’t seem write or doesn’t happen call the vet.
  • Phase Three: At this point the mare will usually lay down and the true labor begins. The feet come through then the nose anything out of this order you should also call the vet. The mare will remain lying do not break the umbilical cord as that breaks naturally.
  • Phase Four: This is the passing of the placenta. Basically another labor stage as she will continue to act like she is colicing. This can be anywhere from a few minutes to hours be patient at this stage as she will still be acting restless after the placenta passes. Check the afterbirth area to make sure all has passed as anything that doesn’t come out can cause infection. If the placenta doesn’t pass also call your vet.

Make sure you are patient with the foal as well the main thing is that the foal is breathing and remove any membranes from around mouth and nose. Have vet come for first checkup to make sure everything is normal. That is pretty much it now the fun begins with youngster take a lots of pics and enjoy.



I have owned over 50 horses and currently own a small horse farm with 8 horses. I have competed on and off for over 25 years while doing mostly trail riding and cow sorting these days. I write these articles to help anyone out there if you love this article pin it to your Pinterest or Share on other social media platform. Thanks for visiting.

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