Now 69mm from crown to rump, the fetus is clearly recognizable as a horse.

The skin remains pale and hairless, and the eyes are still sealed shut, but the internal organs are developing, muscles are growing, hoof-shaped feet are forming and the frog - the rubbery pad on the bottom of the foot which acts as a pump to move blood up the thin length of the horse's leg and back to the heart - is forming.

The sex of the fetus can now be determined. Twins are unusual and unwelcome - mares are not designed to carry two foals to term and vets will usually perform a 'twin reduction' to avoid losing both.
källa:http://2bquarterhorses.webs.com/hintstipsforfoaling.htm