A clinical approach to the diagnosis and treatment of retained fetal membranes with an emphasis placed on the critically ill mare

Retained fetal membranes (RFMs) in mares can be defined as the failure of partial or complete release of the allantochorion by 3 hours after parturition. The incidence of RFM ranges from 2% to 10% of foalings in light breed-type mares, and it has been reported to be as high as 30%-54% in Friesian mares. This peripartum problem occurs specially after dystocia, prolonged gestation, cesarean section, fetotomy, hydropsy, and induced delivery. Uncomplicated abortion, stillbirth, and twinning are not necessarily associated with RFM, unless dystocia also occurs. Occasionally, RFM can occur after an apparent normal foaling for unknown reasons. Many predisposing factors have been postulated: uterine inertia and fatigue, calcium/phosphorus imbalance, selenium deficiency, abnormal hormonal environment, physical mechanical intervention, fescue toxicosis, aging, individual predisposition, and placentitis. This condition can lead to severe problems in mares, including metritis, laminitis, and death. The treatment for this condition can be addressed at three different major levels: uterine clearance, control of shock and endotoxemia, and treatment and prevention of laminitis. This manuscript reviews some of the most relevant articles addressing this reproductive problem and offers the authors' clinical experience on dealing with RFM.