Time Line for Equine Gestation

The normal gestational period for a horse can be between 320 to 360 days. The foal̵7;s health is not only determined by genetics, but also by the quality of care her mother receives. The mare should be kept in a spacious stall and have access to clean water at all times. The mares should receive quality hay or pasture with mineral or vitamin supplements. Providing these resources will help the foal and mare undergo the gestational period healthily.

  1. Day 9

    • In this early stage of gestation, the embryo is about the size of a pinpoint. In an ultrasound, you can spot the embryonic vesicle, which will appear as a small black circle in the mare̵7;s uterus. The vesicle is less than ¼-inch in diameter and looks like a shimmering translucent bubble.

    Day 24

    • Nearing the end of the first month of gestation, you̵7;ll be able to make out the beginnings of animal features on the embryo, such as a head, four buds that will grow into legs and small bumps that will become the eyes. By day 24, the heart should be big enough to spot; it will appear as a tiny black dot resting inside the embryo.

    Day 60

    • By the end of the second month of the pregnancy, the fetus will begin to resemble a horse. Although it will only be the size of hamster, you̵7;ll be able to see the development of tiny hooves, a distinct skull and small triangles that will become the foal̵7;s ears. After this point, the foal will be too large to view on the ultrasound screen.

    Day 100

    • At this point, the fetus will be about 7 inches long̵2;approximately the size of a six-week-old kitten. Hair will start to grow around its lips. The head, which was formerly tucked into its chest, is now untucked so that it is level with the spine and in a normal position. The sex of the foal begins to develop by this point; males will have small lumps that will become the scrotum.

    Day 180

    • The foal will start to gain weight rapidly; it will generally gain more than a pound every 10 days. The fetus will be about the size of a beagle dog at this point and will have hair around its chin, eyelids and muzzle. Mane and tail hairs will also begin to appear.

    Day 320

    • The foal will continue to grow in size and grow hair on its body. In this last week of gestation, its lungs are strong enough to function outside the womb and the legs are sturdy enough to support the foal̵7;s weight. The hair will no longer have a fine, silky texture but rather will have a coarse feel. Around this time, the foal will be ready to be born. The mare will begin to have contractions and her water should break. The horse should be able to give birth naturally, without human intervention.