Shedding of the foetal membranes/placenta is the 3rd and last stage of the parturition process. Normally, the expulsion of the foetal membrane occurs within 3–8 hours after parturition. Retention of the placenta (RoP) is defined as failure to expel foetal membranes within 12-24 hours after parturition. It occurs when the calf’s side of the placenta (the foetal membranes) fails to separate from the mother’s side of the placenta. separation of the membranes normally occurs after the calf is born. Retained foetal membranes are mostly associated with dystocia and metabolic diseases such as milk fever.

Aetiology of Retained Foetal Membranes:

Collagen links the interface between the foetal cotyledons and the maternal caruncles of the uterus. The breakdown of this collagen is likely a key factor in placental separation. Both, the secretion of relaxin and the decline of progesterone, promote collagenase activity necessary for the separation of the foetal membranes.

Secondly, changes in the hormonal environment and maternal recognition of foetal Major Histocompatibility Complex (MHC) Class 1 molecules also play an important role. Apart from this, normal placental expulsion involves a variety of cell types, including neutrophils, T cells, and macrophages. Therefore, impaired migration of neutrophils to the placental interface in the periparturient period can lead to the retention of foetal membranes. The population of proinflammatory macrophage is found to be less in the caruncular tissue of animals with RoP, leading to decreased collagenolysis and fibrinolysis at the cotyledonary-caruncular interface. Animals with RoP have increased cortisol and decreased oestradiol concentrations in late pregnancy, which adversely affects immune functions in affected animals by exerting local and systemic immunosuppressive effects.

Therefore, it can be construed that the lack of placental detachment, rather than insufficient uterine motility, is responsible for the retention of foetal membranes.


Risk Factors:

The following factors make dairy animals prone to retention of foetal membranes/RoP:
1. Advancing age of the cow.
2. Hypocalcaemia.
3. Repeat Breeding.
4. Stillbirth.
5. Placentitis.
6. Premature calving or induction of parturition prematurely.
7. Abortion (particularly with brucellosis or mycotic abortion).
8. Twin birth.
9. Dystocia.
10. Nutritional deficiency.
11. Weak immunity/Immune suppression.
12. Metabolic disorders, especially milk fever.
13. Caesarean section.
14. Infectious diseases: Brucellosis, Leptospirosis, IBR, and BVD.

Potential infection:

Often, the retained foetal membranes come out on their own within 10 days. However, occasionally the retained placenta can lead to serious infections. Therefore, such animals must be kept under observation in a clean & dry environment until they shed those membranes.
If the animal is allowed to sit in mud or manure, the placenta can act as a wick to bring pathogens into the uterus. The uterus can handle a local infection and clean itself, but if the infection goes systemic, then the cow needs to be treated symptomatically.
Furthermore, manual unhooking of the cotyledons from the caruncles can damage the uterus by destroying some of the attachment sites permanently leading to future pregnancy issues such as abortions, premature and stillbirths. Thus, it’s wise to allow the animals to clean themselves so that the placental debris comes out along with the lochia discharge.

Clinical Symptoms:
The retention of foetal membranes is characterized by varying amounts of degenerating, discoloured, and fetid membranes protruding from the vulva for more than 24 hours after parturition. Sometimes, the retained foetal membranes remain inside the uterus and are not visible from the outside. In such a case, the RoP may be confirmed by a foul-smelling discharge. In most cases, there are no clinical signs of systemic illness. When systemic clinical signs are present, they are related to toxaemia.

Diagnosis of Retained Foetal Membranes:
The RoP in a dairy animal can be diagnosed based on history and clinical signs of the foetal membranes protruding from the vulva. Foetal membranes retained within the uterus or projecting into the cervix or vagina can be detected on vaginal examination.

Treatment of Retained Foetal Membranes:
Manual removal of the placenta is no longer recommended and is potentially harmful. Instead, the excess foetal membranes protruding out of the vulva can be trimmed to avoid contamination of the farm and entry of pathogens inside the uterus due to the wick action of the protruding membranes. Untreated cows expel the membranes in 2–11 days with up to 40% of them requiring no treatment at all. An ecbolic preparation with other associated gynecological benefits can be used to hasten the lochial discharge.
Routine use of intrauterine preparations can be avoided unless the case turns into a metritis or pyometra case. The use of oxytocin, oestradiol, PGF2-α, and oral calcium preparations can be helpful in the expulsion of the placenta or prevention of complications. When systemic clinical signs of illness appear, systemic treatment with antimicrobials such as ceftiofur injections is indicated due to its wide spectrum of efficacy.
Prevention of Retained Foetal Membranes in Dairy Herds:
In herds with an unacceptably high incidence of RoP, supplementation with vitamin E and selenium is beneficial. A good mineral mixture supplementation and managing the risk factors mentioned above will be useful in reducing the incidence of retained foetal membrane cases in dairy animals. The use of a suitable anionic mixture preparation around the periparturient period will be useful in risk-prone dairy animals.

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