A horse embryo grows inside the mare’s uterus after fertilization. In the first few weeks, the embryo forms basic organs and limbs. By day 25–30, the heartbeat can be detected. By two months, the embryo is called a fetus and starts to look like a small horse. Over 11 months, it grows steadily until birth. Proper nutrition and care of the pregnant mare are very important to support the healthy growth of the foal.