How Long Is A Mare’s Pregnancy | How Long Is A Horse Pregnant

Summary: A mare’s pregnancy lasts for approximately 335 to 342 days. However, several factors can influence the length of gestation, including breed, age, and the number of foals the mare is carrying.

1. The General Length of Pregnancy in Mares

A mare’s pregnancy typically lasts between 335 and 342 days, which is roughly eleven months. The official average gestation period for mares is 340 days or almost a year, give or take a few weeks. It’s critical to remember that this is just a theoretical approximation since there are several variables that can impact how long a mare carries her foal. In reality, some mares may carry their foals for as little as 320 days, while others may go for around 370 days before giving birth.

While veterinarians can frequently determine the due date using ultrasound and hormone testing, predicting the length of gestation to the day is challenging. The majority of mare owners use an expected due date that is precisely 11 months after breeding to assist them in preparing for foaling as well as ensuring proper veterinary aid is on hand.

It’s also worth noting that mares that have already delivered one foal are more prone to deliver earlier than those that have never given birth before. Breed and mare’s age can also impact the length of gestation.

2. Factors That Can Modify Gestation

Several factors can influence gestation length, including the Mare’s age, previous foaling history, and overall well-being. Mares of different breeds may also have varying gestational lengths. Arabian mares, for example, are known to carry their foals for up to 360 days, whereas Welsh cobs tend to give birth sooner than other breeds, often after just 320 days.

The size of the foal or if there are multiple foals may also play a role in how long a mare’s pregnancy lasts. Abortions, premature births, and stillbirths can alter gestation length. Factors such as uterine infection, hormonal imbalances, thyroid dysfunction, and poor nutrition can also have an impact on the duration of gestation.

Stress, particularly during late gestation, can cause mares to carry their foals for more extended periods than they would otherwise. As a result, mare owners must keep their horses’ well-being in mind throughout the entire pregnancy.

3. Tracking a Mare’s Gestation Length

A mare’s gestational period can be tracked in various ways, including via ultrasound and hormone screening. Ultrasonography allows the veterinarian to visualize the foal’s growth and development inside the mare’s uterus. Hormone measurement tests measure hormone levels such as progesterone and estrogen to detect pregnancy and estimate foal development.

A mare’s rectal temperature may also be used to predict when she will foal. A mare’s temperature typically falls sharply before delivery. Temperature monitoring alone is insufficient to pinpoint the precise time of foaling, but it aids in alerting horse owners and veterinarians that foaling is imminent. Observing the mare’s behavior, such as restlessness and frequent urination, as well as the waxing and waning of the teats, can also help owners anticipate foaling within a day or two.

Mare owners should work with experienced veterinarians and breeding professionals to track their mare’s gestational length accurately, ensuring that they’re prepared for foaling and ready to address any concerns that may arise.

4. Preparing for Foaling

A mare should be kept healthy with a balanced diet and exercise regimen throughout her pregnancy to reduce the likelihood of complications during foaling. Owners should also ensure that their horse is getting enough minerals, vitamins, and vital nutrients such as calcium, which helps build strong bones in the foal.

The mare’s stall should be cleaned frequently, with fresh bedding and food provided regularly. The stall should have sufficient room for the mare to lie down comfortably, as well as sufficient ventilation to prevent respiratory problems in both the mare and the foal.

In addition to routine veterinary checkups, mares due to give birth soon should be monitored constantly and watched for signs of foaling. It’s important to have a plan in place for taking care of both the mare and foal after delivery, including contacting a veterinarian, cleaning and disinfecting the newborn foal, and ensuring proper feeding.


A mare’s pregnancy typically lasts between 335 and 342 days, although this can vary depending on several factors. The gestational length of the mare can be influenced by age, breed, history, and overall well-being, making it crucial to keep an eye on these factors throughout the pregnancy. Monitoring a mare’s rectal temperature, behavior, and udders, as well as consulting with experienced veterinarians and breeding professionals, can help anticipate foaling and identify any issues that may arise. Proper nutrition, exercise, comfortable housing, and regular veterinary care can help prepare the horse for successful foaling.

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