Examination of the Fetal Membranes in Horses

Fetal membranes that are not expelled within 3 hr of parturition are considered to be retained. Fetal membrane retention may be complete, but commonly only the nongravid horn is retained. If the typically puckered nongravid tip is not observed, it is assumed to be retained. If any membranes are hanging from the vulva of a postpartum mare, the amnion and cord should not be cut and removed, because their weight provides tension thought to enhance placental separation and expulsion. Fetal membranes not passed within 3–10 hr are considered to be pathologic and can lead to metritis, endotoxemia, and subsequently laminitis with fatal results. Accordingly, it is prudent to treat the condition as potentially serious. If dystocia or traumatic uterine manipulation has occurred, aggressive treatment for retained membranes should be instituted immediately after parturition.

For early (3–8 hr) retention, 10–20 IU oxytocin can be repeatedly administered IV or IM every 30 min until the fetal membranes have passed. The dose of oxytocin should be decreased if the mare shows severe signs of colic or discomfort. Milking or sucking also stimulates endogenous release of oxytocin. Mares that retain fetal membranes >8 hr should be administered broad-spectrum antibiotics, such as potassium penicillin (22,000–44,000 IU/kg, IV, qid), gentamicin (2.2 mg/kg, IV, qid), or flunixin meglumine (0.25–0.5 mg/kg, IV, tid).