• Fetal membranes are comprised of the allantochorion (placenta), amnion and umbilical cord.
• Fetal membranes are said to be retained if they are not passed in their entirety within 3-6 h post-partum.
• The placenta is classed as retained if it has not passed within 3-6 h post-partum.
• The placenta in the non-gravid horn of the uterus is most often retained.
• Most common after dystocia   Reproduction: dystocia  , induction of parturition   Reproduction: parturition - induction  , Cesarean section   Uterus: caesarean section  or abortion   Abortion: overview  .
• Cause: often unknown; can follow apparently normal foalings but can also be associated with dystocia, atony, twins, etc.
• Signs: sometimes the membranes may be seen protruding from the vulva post-foaling. In cases where only a small portion is retained, no membranes are visible externally and the mare may present with signs of endotoxemia 24-48 h post-foaling.
• Diagnosis: vaginal examination, transrectal ultrasonography.
• Treatment: depends on duration of retention and presence/absence of metritis-laminitis-septicemia complex. Manual traction, the use of hormones, eg oxytocin, or by uterine infusion.
• Antimicrobial therapy, is required in most cases and sometimes anti-inflammatory therapy as well.
• Intrauterine manipulation should be kept to a minimum in order to reduce the risk of complications developing.
• Prognosis: good to guarded.

Presenting signs

• Placental membranes visible hanging from the vulva 3-6 h post-partum     .
• Expelled placental membranes found to have some areas missing, usually in the area of the 'non-gravid' horn, ie the horn opposite to that in which the foal was lying.
• If not detected initially, the mare may become dull, inappetant and have reduced milk production within 24-48 h.

Acute presentation

• Mostly normal.
• Dull, depressed mare.
• Fever.

Breed/Species predisposition

• Heavy draft breeds.
• Metritis-laminitis-septicemia complex   Metritis-laminitis-septicemia complex  : heavy breeds.

Cost considerations

• Removal of placenta by a veterinary surgeon.
• Antibiotic therapy.
• Multiple examinations with repeated uterine lavage.
• Potential hospitalization of mare and foal for severe cases of endotoxemia.
• Milk supplementation or even fostering of foals with very sick dams.
• Metritis-laminitis-toxemia syndrome.