What complications may occur in a mare who has not properly passed the placenta after foaling?

Answer 1

In the US this is most frequently referred to as a retained placenta.

Founder is probably the most frequently discussed complication of a retained placenta, followed by sepsis (infection that spreads throughout the body) and infection. Severe illness usually ensues within several hours or a few days, and can quickly be fatal. Veterinary care is vital for a retained placenta and its complications.

When a mare retains part or all of the placenta after foaling, also known as a 'hung cleansing', several complications can arise. The most problematic is severe infection. This happens in many cases because the placenta, after foaling, dies and begins to break down. The large amount of decomposing tissue in her uterus can make a mare extremely ill. Depending on what sort of infection she develops and how far it spreads, it can also cause scarring inside her uterus and vagina; this can prevent her from conceiving or from carrying a foal to term in the future.

Another common complication is mastitis; this occurs both because of the strain on the mare's immune system caused by the decomposing tissue inside her, and because the discharge of pus and infected fluids from her vagina will trickle between her legs to her udder. Mastitis is an infection of the udder that leads to pain, swelling and heat in the udder, and also 'poisons' her milk. A mare with mastitis cannot feed her foal until the condition has cleared up, and will sometimes 'dry up' so that the foal must be bottle fed not just for a few days, but until it can be weaned.

There are photographs readily available on the internet of what a complete horse placenta looks like, so after your mare has foaled it is good practise to examine the placenta to make sure it is intact. Obvious torn edges could show where a part has come away, possibly meaning that she has retained some of it. The placenta is normally passed within a few hours of foaling, and certainly within a day; a mare who has not passed it may be off her food or listless, and may develop a fever and a bad-smelling discharge from her vagina. If you suspect that your mare has retained part or all of her placenta, CALL THE VET immediately. Removing a retained placenta a day or two after foaling is easy and usually has a good outcome. Hanging about to 'wait and see' may not.