Retained fetal membranes that haven’t passed within three hours of parturition are true emergencies. They occur most commonly after dystocia/obstetrical manipulation, induction of labor, and abortion, as well as in certain breeds such as Friesians. If a mare retains the fetal membranes once, she has a higher chance of retained fetal membranes in subsequent pregnancies.
Oxytocin
“Start simple by administering oxytocin,” said Melissa Prell, DVM, MS, Dipl. ACT, director at Peterson Smith Advanced Fertility Center, in Summerfield, Florida, during a Burst Session at the 2023 AAEP Convention in San Diego. “But remember they’re going to have an increased number of oxytocin receptors at time of foaling, so the mares may be a little more sensitive to it. Start with a lower dose of 10 units. If the mare tolerates it well, you can increase it to the regular dose of 20 units. This can even be repeated in an hour for a few doses.”
Uterine Lavage
If oxytocin is not successful, move on to uterine lavage.
“The retained fetal membranes are a great nidus for bacterial growth, with subsequent endotoxemia and perhaps even a laminitic episode in the mare,” Prell said. “Lavaging the uterus decreases bacteria load and aids in the release of the membranes. Start antibiotics if the membranes do not pass within six to 12 hours.
“Use a nasogastric tube and stomach pump to infuse water with dilute betadine solution into the allantoic cavity,” she continued. “The uterus will reinflate, and this will help the tiny microcotyledons on the chorioallantois release from their attachments.”
Dutch Technique
Alternatively, consider the Dutch technique. Make an incision on any of the umbilical vessels in the cord and insert a stallion catheter up the vessel. Connect the stallion catheter to a garden hose with a nozzle to regulate the flow of water, and very slowly begin infusing water over five to 10 minutes into the vasculature of the fetal membranes. Again, this causes edema within the membranes, encouraging the microcotyledons to release. Carefully manipulating the membranes can prove beneficial, but one should never pull, said Prell. Pulling can result in further tearing of the membranes within the uterus, making it more difficult to remove all the pieces and/or causing intussusception of a uterine horn or even uterine prolapse.
