How Can I Tell If My Mare Is Pregnant?

While determining whether a mare is pregnant is a very important part of horse breeding, it can be relatively difficult to accomplish. Most mares show few physical signs of pregnancy until late in the process. Any early detection of pregnancy necessitates the skills of a veterinarian to be certain that the insemination took hold. Early detection of pregnancy is important not only to make the most of the breeding season, but also to get advance warning if a mare is pregnant with twins, which can be a problematic situation.

  1. Early Signs

    • One of the keys to establishing pregnancy early on for your mare is to know when she was bred. If you monitored the breeding and made note of when it took place, you will have a better idea of when certain tests can be performed to check for pregnancy. The most reliable early method of detection for horses is ultrasound. In some cases, a veterinarian can confirm pregnancy by use of an ultrasound as early as 10 to 11 days after ovulation. However, most veterinarians prefer to wait at least 13 to 15 days after ovulation before performing an ultrasound. The early days of pregnancy for a horse are tenuous. There is a 10 to 15 percent chance in the first month that the mother's body will reabsorb the embryo. It is often recommended that pregnancy be reconfirmed at 45, 60, and even 90 days to be certain that the developing foal was not reabsorbed. Pregnancy can be reconfirmed by trans-rectal palpation or ultrasound. A veterinarian should perform either procedure to be certain of the accuracy of the results as well as being certain that no harm is done to the mare.

    Twins

    • Not only for the purpose of your breeding program, but also for the health of mother and foals, it is important to discover whether the mare is carrying twins as early in the pregnancy as possible. This would be done by ultrasound at 14 to 16 days after ovulation. A twin pregnancy poses multiple risks. One or both embryos are reabsorbed by the mare's body within the first 60 days in 95 percent of these pregnancies. Letting them reabsorb naturally can damage the possibility of the mare conceiving again during that breeding season and having a normal pregnancy. Few twin embryos survive past 50 days in the womb, and of those that do, many will spontaneously abort around six to eight months. Of the small percentage that survive this, it is exceptionally unusual for two healthy foals to be born. The likelihood of either surviving is slim, but if one, or even both, does survive, it's likely that the foal will be small and weak.

    Last Trimester

    • The last trimester is when physical changes begin to become obvious. It is at this point that you will notice the enlargement of the mare's belly and a decrease in activity levels. In the final few weeks of the pregnancy, you will notice the foal "drop," very similar to pregnant women. The mare's udder will not begin to enlarge until the final two weeks of her pregnancy, with the teats filling out in the last week and beginning to secrete fluid.