Probably the most common condition that affects mares after foaling is septic metritis, which is an infection in the uterus. These uterine infections can affect the mare's health and can even lead to death if not treated immediately. Many times mares develop an infection after a difficult birth or if the mare fails to pass the afterbirth. If the afterbirth is not passed after 3 hours, it is considered to be retained and the condition should be treated. However, removing the placenta by hand is not recommended as the mare's uterus is very sensitive and removing the placenta can cause severe uterine damage and can even tear the uterus. A retained placenta in a mare is a reason to call your veterinarian. Most of the time, the placenta can be expelled with injections of oxytocin or flushing the uterus with sterile fluids.

Mares that have had retained placentas are susceptible to laminitis or founder but if the uterus is flushed well and infection is prevented, the chance of laminitis is decreased. If a mare develops a discharge after foaling and also develops a uterine infection, then the chance of laminitis is greater and it is critical that the mare be examined. These infections can cause the mares to be toxic, and these toxins can lead to death. Generally, antibiotics are indicated as well as large volume flushes of the uterus; sometimes keeping these mares on soft sand may help to prevent laminitis. Another possible prevention for laminitis is to ice the horse's feet 24 hours a day for 2 to 3 days. However, removing the infected fluid from the uterus is critical. If you have a mare that retained her placenta or had a difficult birth, call your veterinarian to examine her and make sure she is okay.