Retained fetal* membranes (RFMs) is a condition that commonly affects mares after foaling. Stage three of parturition is expulsion of the placenta (fetal membranes), which should occur within three hours of giving birth. After this time the membranes are considered to be retained, and veterinary intervention is required if they have still not been passed six hours after parturition.
The normal process of giving birth triggers a sequence of events that lead to the expulsion of the placenta. Any interruption to this normal process of parturition can increase the likelihood of the placenta being retained. For example, abortion, difficulty giving birth (dystocia), twin pregnancies and Caesarian section are all examples of abnormal parturition, and the incidence of RFMs is much higher in these cases. Occasionally mares that undergo a normal parturition can retain the placenta.
If the mare has retained the whole of the placenta, this is very obvious as it can be seen hanging out of the vulva under the tail. It is a good idea, if the membranes are dragging on the floor, to tie them up with a bit of rope or twine to prevent the mare from stepping on them. However, some mares retain a small part of the placenta only. This can be detected by examining the placenta that has been passed, looking for tears or bits missing. Unfortunately this requires a bit of practice, to be able to correctly identify the different parts of the placenta in order to identify if there are any parts missing. If you have any concerns that the placenta is retained, either in whole or part, please contact your veterinarian.
RFMs is a concern because it can lead to further complications, including septic metritis (infection of the uterus), septicaemia (infection of the blood) and endotoxaemia (toxins in the blood), laminitis, and death. Heavy draught-type mares are more susceptible to these complications, but any mare can suffer from them. If the retained membranes are removed within 6-12 hours of parturition, the chance of these complications occurring is greatly reduced.
In most cases the membranes detach quickly in response to the administration of oxytocin, which causes uterine contractions. Sometimes repeat doses of oxytocin are required. However, if this fails there are several methods employed to physically remove the placenta, which must be performed by the veterinarian as there is a risk of causing the uterus to tear, prolapse or haemorrhage. These include twisting the placenta into a rope and moving the hand between the uterus and the placenta to separate them, or filling the uterus with fluid to separate off the placenta. Once the placenta has been removed, your veterinarian should check it to ensure the whole placenta is there. If there are any pieces remaining in the uterus, these need to be removed. However, as the uterus is quite a large structure after giving birth, it is not always possible to reach all the way to the tips of the uterine horns, where the placenta most commonly remains attached. A second visit in a few hours time may be necessary, when the uterus will have involuted (shrunk) a little bit.
Depending on how long the membranes were retained for, and how contaminated the uterus is, it may be advisable to put the mare on a course of antibiotics. Another very important aspect of treatment in such cases is uterine lavage, where the uterus is flushed with a solution, such as dilute iodine (betadine) solution or sterile saline, to remove any abnormal discharge and bacteria. This may need to be repeated daily or every second day until the fluid coming back out of the uterus is clear. If the mare is not up to date with her tetanus vaccinations, she should receive a booster vaccination. Anti-inflammatories are also recommended, such as phenylbutazone (bute).
The prognosis for the health of the mare as well as fertility is good, providing complications are avoided, such as metritis. Early intervention is the key.
*Fetus/fetal have been spelt this way on purpose. These are commonly acknowledged to be the North American spelling of the words, but are actually the correct way to spell them.
