The placenta is usually expelled 15 min to 1 hour after birth but may take up to 3 hours without a problem to the mare. If the placenta is not expelled or it tears and a portion remains within the mare it can lead to very severe problems and death of the mare. The placenta can act as a wick and draw bacteria into the uterus and as it dies provide a substrate for bacterial growth which will progress and spread throughout the mare. Because the placenta can tear and a portion retained within the mare it is essential to check it carefully. The placenta is Y shapped and needs to be spread out to see entire placenta. The placenta will usually be delivered inside-out. The velvety red side (usually now on the inside) was once attached to the uterine wall. Be sure to turn the placenta completely inside-out if it is not that way. Sometimes the last portion delivered may still remain right side out. Stretch both horns out and lay it out as in the image below. Examine the placenta to make sure it is complete up both horns. The clear portion is the amnion and is sometimes attached or may break off with the foal. Unusual white spots, red spots, or change in color of one portion of the placenta may indicate a problem and you should save the placenta and consult your veterinarian in case the foal needs to be give antibiotics.
If the placenta is not delivered within 2 hours the following sequence should be followed:
A problem does not really develop until the placenta is retained for 8 - 12 hours so calling the veterinarian at 4 hour will ensure prompt care for your mare. It is obvious from the above that oxytocin should be kept on hand when mares are foaling. When ariving, the veterinarian will usually infusion 5 - 10 liters of water or saline + betadine into uterus. The fluid will be kept in the uterus for 5 - 10 minutes to cause the placenta to release and it is then usually delivered shortly after allowing the uterus to drain. Antibiotics and anti-inflamatory/pain drugs such as bantamine are given. Infections from retained placenta's that become systemic often lead to laminitis even if the mare survives more aggressive therapy.
The causes of retained placenta are:
The mare owner or attendent need not be concerned if the placenta is still hanging down from the mare when she stands up as in the image below. The placenta should simply be tied up in a knot to prevent the mare from stepping on it. Usually after the foal gets up and nurses, oxytocin is naturally released, the mare will lie down or remain standing and the placenta will be delivered.