Periparturient haemorrhage

Periparturient haemorrhage describes blood loss prior to, during or post parturition. The clinical presentation can range from sub-clinical to sudden death depending on the degree of haemorrhage.
The uterus is supplied by 6 main arteries. The left and right utero-ovarian artery originates from the aorta. The left and right middle uterine artery originates from the external iliac artery and the left and right caudal uterine artery originates from the internal pudendal artery. If the haemorrhage is contained within the broad ligament or within the endometrial wall, there is an increased chance of successful tamponade. However, if the haemorrhage occurs proximal to the ovary (i.e. outside of the broad ligament), or the broad ligament fails to contain the haemorrhage, blood loss into the abdomen will occur without any tendency for compression, and the formation of a viable clot is less likely. Blood loss into the uterus is possible if uterine artery rupture and uterine wall failure occur together, and haemorrhagic discharge from the uterus may be dramatic in a few cases.
Haemorrhage around foaling affects 2–3% of mares and is responsible for around 40% of deaths of mares around parturition. Although haemorrhage can occur in mares of any age it tends to occur in multiparous mares of middle to older age. Each haemorrhagic event causes fibrosis and a loss of arterial elasticity, so mares that have had a previous haemorrhage are predisposed in future pregnancies. Other risk factors for haemorrhage are dystocia, uterine prolapse, uterine torsion and decreased copper levels. […]