Illustration of a normal anterior presentation with a dorsosacral position and normal posture (head resting on the knees). This configuration is most efficient in dilating the birth canal.
This near-term fetus is in a transverse ventral presentation and in a left cephalo-ilial position. This is a rare presentation because the curvature of the back of the fetus does not conform with the curvature of the uterus.
This fetus is in a transverse dorsal presentation and in left cephalo-ilial position. The presentation need not be symmetrical as shown in this drawing. It may be difficult to determine whether the head is near the left or the right ilium of the mare. All one may be able to palpate is the curvature of the back. This is a rare presentation. The head and the front legs are in one horn, the hindlegs in the opposite horn.
During the third trimester the equine fetus is normally in a dorsopubic position. The fetus rotates to the dorsosacral position during the final couple of days of gestation in which it is assisted by the rolling of the mare.
During the third trimester the equine fetus is normally in a dorsopubic position. The fetus rotates to the dorsosacral position during the final couple of days of gestation.
Anterior presentation, dorsosacral position, abnormal posture as the hindlegs are extended forwards and are entering the pelvic inlet. Difficult to correct. As the hind feet are repelled into the uterus they may impact below the pubic brim upon subsequent traction and puncture the wall of the uterus.
Anterior presentation, dorsosacral position, abnormal posture as the hindlegs are extended forwards, and are entering the pelvic inlet. Difficult to correct. As the hind feet are repelled into the uterus they may impact below the pubic brim upon subsequent traction and puncture the wall of the uterus.
Occasionally the tip of the nose of the fetus is deflected downwards by the pubic brim during entry into the birth canal. Strong uterine and abdominal contractions then force the nape of the neck into the pelvic inlet. Correction consists of repulsion of the poll of the head and elevation of the muzzle.